Boost.Regex John Maddock Copyright © 1998-2010 John Maddock

Distributed under the Boost Software License, Version 1.0. (See accompanying ®le LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Table of Contents

Con®guration ...... 3 Compiler Setup ...... 3 Locale and traits class selection ...... 3 Linkage Options ...... 3 Algorithm Selection ...... 4 Algorithm Tuning ...... 4 Building and Installing the Library ...... 5 Introduction and Overview ...... 7 Unicode and Boost.Regex ...... 9 Understanding Marked Sub-Expressions and Captures ...... 10 Partial Matches ...... 14 Regular Expression Syntax ...... 17 Perl Regular Expression Syntax ...... 17 POSIX Extended Regular Expression Syntax ...... 29 POSIX Basic Regular Expression Syntax ...... 36 Character Class Names ...... 40 Character Classes that are Always Supported ...... 40 Character classes that are supported by Unicode Regular Expressions ...... 41 Collating Names ...... 43 Digraphs ...... 43 POSIX Symbolic Names ...... 43 Named Unicode Characters ...... 46 The Leftmost Longest Rule ...... 46 Search and Replace Format String Syntax ...... 48 Sed Format String Syntax ...... 48 Perl Format String Syntax ...... 48 Boost-Extended Format String Syntax ...... 50 Reference ...... 53 basic_regex ...... 53 match_results ...... 64 sub_match ...... 72 regex_match ...... 84 regex_search ...... 88 regex_replace ...... 91 regex_iterator ...... 95 regex_token_iterator ...... 101 bad_expression ...... 109 syntax_option_type ...... 110 syntax_option_type Synopsis ...... 110 Overview of syntax_option_type ...... 111 Options for Perl Regular Expressions ...... 111 Options for POSIX Extended Regular Expressions ...... 113 Options for POSIX Basic Regular Expressions ...... 116 Options for Literal Strings ...... 118

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match_¯ag_type ...... 118 error_type ...... 122 regex_traits ...... 123 Interfacing With Non-Standard String Types ...... 124 Working With Unicode and ICU String Types ...... 124 Introduction to using Regex with ICU ...... 124 Unicode regular expression types ...... 124 Unicode Regular Expression Algorithms ...... 126 Unicode Aware Regex Iterators ...... 127 Using Boost Regex With MFC Strings ...... 133 Introduction to Boost.Regex and MFC Strings ...... 133 Regex Types Used With MFC Strings ...... 133 Regular Expression Creation From an MFC String ...... 133 Overloaded Algorithms For MFC String Types ...... 134 Iterating Over the Matches Within An MFC String ...... 136 POSIX Compatible C API©s ...... 138 Concepts ...... 141 charT Requirements ...... 141 Traits Class Requirements ...... 142 Iterator Requirements ...... 145 Deprecated Interfaces ...... 146 regex_format (Deprecated) ...... 146 regex_grep (Deprecated) ...... 147 regex_split (deprecated) ...... 151 High Level Class RegEx (Deprecated) ...... 153 Internal Details ...... 159 Unicode Iterators ...... 159 Background Information ...... 162 Headers ...... 162 Localization ...... 162 Thread Safety ...... 170 Test and Example Programs ...... 170 References and Further Information ...... 172 FAQ ...... 172 Performance ...... 173 Standards Conformance ...... 174 Redistributables ...... 176 Acknowledgements ...... 176 History ...... 177

A printer-friendly PDF version of this manual is also available.

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Configuration Compiler Setup

You shouldn©t need to do anything special to con®gure Boost.Regex for use with your compiler - the Boost.Con®g subsystem should already take care of it, if you do have problems (or you are using a particularly obscure compiler or platform) then Boost.Con®g has a con®gure script that you can run. Locale and traits class selection

The following macros (see user.hpp) control how Boost.Regex interacts with the user©s locale:

macro description

BOOST_REGEX_USE_C_LOCALE Forces Boost.Regex to use the global C locale in its traits class support: this is now deprecated in favour of the C++ locale.

BOOST_REGEX_USE_CPP_LOCALE Forces Boost.Regex to use std::locale in it©s default traits class, regular expressions can then be imbued with an instance speci®c locale. This is the default behaviour on non-Windows platforms.

BOOST_REGEX_NO_W32 Tells Boost.Regex not to use any Win32 API©s even when available (implies BOOST_REGEX_USE_CPP_LOCALE unless BOOST_REGEX_USE_C_LOCALE is set).

Linkage Options

macro description

BOOST_REGEX_DYN_LINK For Microsoft and Borland C++ builds, this tells Boost.Regex that it should link to the dll build of the Boost.Regex. By default boost.regex will link to its static library build, even if the dynam- ic C runtime library is in use.

BOOST_REGEX_NO_LIB For Microsoft and Borland C++ builds, this tells Boost.Regex that it should not automatically select the library to link to.

BOOST_REGEX_NO_FASTCALL For Microsoft builds, this tells Boost.Regex to use the __cdecl calling convention rather than __fastcall. Useful if you want to use the same library from both managed and unmanaged code.

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Algorithm Selection

macro description

BOOST_REGEX_RECURSIVE Tells Boost.Regex to use a stack-recursive matching algorithm. This is generally the fastest option (although there is very little in it), but can cause stack over¯ow in extreme cases, on Win32 this can be handled safely, but this is not the case on other platforms.

BOOST_REGEX_NON_RECURSIVE Tells Boost.Regex to use a non-stack recursive matching algorithm, this can be slightly slower than the alternative, but is always safe no matter how pathological the regular expression. This is the default on non-Win32 platforms.

Algorithm Tuning

The following option applies only if BOOST_REGEX_RECURSIVE is set.

macro description

BOOST_REGEX_HAS_MS_STACK_GUARD Tells Boost.Regex that Microsoft style __try - __except blocks are supported, and can be used to safely trap stack over¯ow.

The following options apply only if BOOST_REGEX_NON_RECURSIVE is set.

macro description

BOOST_REGEX_BLOCKSIZE In non-recursive mode, Boost.Regex uses largish blocks of memory to act as a stack for the state machine, the larger the block size then the fewer allocations that will take place. This defaults to 4096 bytes, which is large enough to match the vast majority of regular expressions without further allocations, however, you can choose smaller or larger values depending upon your platforms characteristics.

BOOST_REGEX_MAX_BLOCKS Tells Boost.Regex how many blocks of size BOOST_REGEX_BLOCKSIZE it is permitted to use. If this value is exceeded then Boost.Regex will stop trying to ®nd a match and throw a std::runtime_error. Defaults to 1024, don©t forget to tweek this value if you alter BOOST_REGEX_BLOCKSIZE by much.

BOOST_REGEX_MAX_CACHE_BLOCKS Tells Boost.Regex how many memory blocks to store in it©s internal cache - memory blocks are taken from this cache rather than by calling ::operator new. Generally speeking this can be an order of magnitude faster than calling ::opertator new each time a memory block is required, but has the downside that Boost.Regex can end up caching a large chunk of memory (by default up to 16 blocks each of BOOST_REGEX_BLOCKSIZE size). If memory is tight then try de®ning this to 0 (disables all caching), or if that is too slow, then a value of 1 or 2, may be suf®cient. On the other hand, on large multi-processor, multi- threaded systems, you may ®nd that a higher value is in order.

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Building and Installing the Library

When you extract the library from its zip ®le, you must preserve its internal directory structure (for example by using the -d option when extracting). If you didn©t do that when extracting, then you©d better stop reading this, delete the ®les you just extracted, and try again!

This library should not need con®guring before use; most popular compilers/standard libraries/platforms are already supported "as is". If you do experience con®guration problems, or just want to test the con®guration with your compiler, then the process is the same as for all of boost; see the con®guration library documentation.

The library will encase all code inside namespace boost.

Unlike some other template libraries, this library consists of a mixture of template code (in the headers) and static code and data (in cpp ®les). Consequently it is necessary to build the library©s support code into a library or archive ®le before you can use it, instructions for speci®c platforms are as follows:

Building with bjam

This is now the preferred method for building and installing this library, please refer to the getting started guide for more information.

Building With Unicode and ICU Support

Boost.Regex is now capable of performing a con®guration check to test whether ICU is already installed in your compiler©s search paths. When you build you should see a message like this:

Performing configuration checks

- has_icu builds : yes

Whick means that ICU has been found, and support for it will be enabled in the library build.

Tip

If you don©t want the regex library to use ICU then build with the "--disable-icu" command line option.

If instead you see:

Performing configuration checks

- has_icu builds : no

Then ICU was not found and support for it will not be compiled into the library. If you think that it should have been found, then you will need to take a look at the contents of the ®le boost-root/bin.v2/con®g.log for the actual error messages obtained when the build carried out the con®guration check. You will then need to ®x these errors by ensuring your compiler gets invoked with the correct options, for example:

bjam include=some-include-path --toolset=toolset-name install will add "some-include-path" to your compilers header include path, or if ICU has been built with non-standard names for it©s binaries, then:

bjam -sICU_LINK="linker-options-for-icu" --toolset=toolset-name install

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Will use "linker-options-for-icu" when linking the library rather than the default ICU binary names.

You might also need to use the options "cxx¯ags=-option" and "link¯ags=-option" to set compiler and linker speci®c options.

Important

Con®guration results are cached - if you try rebuilding with different compiler options then add an "-a" to the bjam command line to force all targets to be rebuilt.

If ICU is not already in your compiler©s path, but instead headers, libraries and binaries are located at path-to-icu/include, path-to- icu/lib and path-to-icu/bin respectively then you need to set the environment variable ICU_PATH to point to the root directory of your ICU installation: this typically happens if you©re building with MSVC. For example if ICU was installed to c:\download\icu you might use:

bjam -sICU_PATH=c:\download\icu --toolset=toolset-name install

Important

ICU is a C++ library just like Boost is, as such your copy of ICU must have been built with the same C++ compiler (and compiler version) that you are using to build Boost. Boost.Regex will not work correctly unless you ensure that this is the case: it is up to you to ensure that the version of ICU you are using is binary compatible with the toolset you use to build Boost.

And ®nally, if you want to build/test with multiple compiler versions, all with different ICU builds, then the only way to achieve that currently is to modify your user-con®g.jam so that each toolset has the necessary compiler/linker options set so that ICU is found automatically by the con®guration step (providing the ICU binaries use the standard names, all you have to add is the appropriate header-include and linker-search paths).

Building from Source

The Regex library is "just a bunch of source ®les": nothing special is required to build them.

You can either build the ®les under boost-path/libs/regex/src/*.cpp as a library, or add them directly to your project. This is particularly useful if you need to use speci®c compiler options not supported by the default Boost build.

There are two #de®nes you should be aware of:

· BOOST_HAS_ICU should be de®ned if you want ICU support compiled in.

· BOOST_REGEX_DYN_LINK should be de®ned if you are building a DLL on Windows.

Important

The make®les that were supplied with Boost.Regex are now deprecated and will be removed in the next release.

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Introduction and Overview

Regular expressions are a form of pattern-matching that are often used in text processing; many users will be familiar with the Unix utilities grep, sed and awk, and the programming language Perl, each of which make extensive use of regular expressions. Traditionally C++ users have been limited to the POSIX C API©s for manipulating regular expressions, and while Boost.Regex does provide these API©s, they do not represent the best way to use the library. For example Boost.Regex can cope with wide character strings, or search and replace operations (in a manner analogous to either sed or Perl), something that traditional C libraries can not do.

The class basic_regex is the key class in this library; it represents a "machine readable" regular expression, and is very closely modeled on std::basic_string, think of it as a string plus the actual state-machine required by the regular expression algorithms. Like std::basic_string there are two typedefs that are almost always the means by which this class is referenced:

namespace boost{

template > class basic_regex;

typedef basic_regex regex; typedef basic_regex wregex;

}

To see how this library can be used, imagine that we are writing a credit card processing application. Credit card numbers generally come as a string of 16-digits, separated into groups of 4-digits, and separated by either a space or a hyphen. Before storing a credit card number in a database (not necessarily something your customers will appreciate!), we may want to verify that the number is in the correct format. To match any digit we could use the regular expression [0-9], however ranges of characters like this are actually locale dependent. Instead we should use the POSIX standard form [[:digit:]], or the Boost.Regex and Perl shorthand for this \d (note that many older libraries tended to be hard-coded to the C-locale, consequently this was not an issue for them). That leaves us with the following regular expression to validate credit card number formats:

(\d{4}[- ]){3}\d{4}

Here the parenthesis act to group (and mark for future reference) sub-expressions, and the {4} means "repeat exactly 4 times". This is an example of the extended regular expression syntax used by Perl, awk and egrep. Boost.Regex also supports the older "basic" syntax used by sed and grep, but this is generally less useful, unless you already have some basic regular expressions that you need to reuse.

Now let©s take that expression and place it in some C++ code to validate the format of a credit card number:

bool validate_card_format(const std::string& s) { static const boost::regex e("(\\d{4}[- ]){3}\\d{4}"); return regex_match(s, e); }

Note how we had to add some extra escapes to the expression: remember that the escape is seen once by the C++ compiler, before it gets to be seen by the regular expression engine, consequently escapes in regular expressions have to be doubled up when embedding them in C/C++ code. Also note that all the examples assume that your compiler supports argument-dependent-lookup lookup, if yours doesn©t (for example VC6), then you will have to add some boost:: pre®xes to some of the function calls in the examples.

Those of you who are familiar with credit card processing, will have realized that while the format used above is suitable for human readable card numbers, it does not represent the format required by online credit card systems; these require the number as a string of 16 (or possibly 15) digits, without any intervening spaces. What we need is a means to convert easily between the two formats, and this is where search and replace comes in. Those who are familiar with the utilities sed and Perl will already be ahead here; we need two strings - one a regular expression - the other a "format string" that provides a description of the text to replace the match

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// match any format with the regular expression: const boost::regex e("\\A(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})\\z"); const std::string machine_format("\\1\\2\\3\\4"); const std::string human_format("\\1-\\2-\\3-\\4");

std::string machine_readable_card_number(const std::string s) { return regex_replace(s, e, machine_format, boost::match_default | boost::format_sed); }

std::string human_readable_card_number(const std::string s) { return regex_replace(s, e, human_format, boost::match_default | boost::format_sed); }

Here we©ve used marked sub-expressions in the regular expression to split out the four parts of the card number as separate ®elds, the format string then uses the sed-like syntax to replace the matched text with the reformatted version.

In the examples above, we haven©t directly manipulated the results of a regular expression match, however in general the result of a match contains a number of sub-expression matches in addition to the overall match. When the library needs to report a regular expression match it does so using an instance of the class match_results, as before there are typedefs of this class for the most common cases:

namespace boost{

typedef match_results cmatch; typedef match_results wcmatch; typedef match_results smatch; typedef match_results wsmatch;

}

The algorithms regex_search and regex_match make use of match_results to report what matched; the difference between these algorithms is that regex_match will only ®nd matches that consume all of the input text, where as regex_search will search for a match anywhere within the text being matched.

Note that these algorithms are not restricted to searching regular C-strings, any bidirectional iterator type can be searched, allowing for the possibility of seamlessly searching almost any kind of data.

For search and replace operations, in addition to the algorithm regex_replace that we have already seen, the match_results class has a format member that takes the result of a match and a format string, and produces a new string by merging the two.

For iterating through all occurences of an expression within a text, there are two iterator types: regex_iterator will enumerate over the match_results objects found, while regex_token_iterator will enumerate a series of strings (similar to perl style split operations).

For those that dislike templates, there is a high level wrapper class RegEx that is an encapsulation of the lower level template code - it provides a simpli®ed interface for those that don©t need the full power of the library, and supports only narrow characters, and the "extended" regular expression syntax. This class is now deprecated as it does not form part of the regular expressions C++ standard library proposal.

The POSIX API functions: regcomp, regexec, regfree and [regerr], are available in both narrow character and Unicode versions, and are provided for those who need compatibility with these API©s.

Finally, note that the library now has run-time localization support, and recognizes the full POSIX regular expression syntax - including advanced features like multi-character collating elements and equivalence classes - as well as providing compatibility with other regular expression libraries including GNU and BSD4 regex packages, PCRE and Perl 5.

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Unicode and Boost.Regex

There are two ways to use Boost.Regex with Unicode strings:

Rely on wchar_t

If your platform©s wchar_t type can hold Unicode strings, and your platform©s C/C++ runtime correctly handles wide character constants (when passed to std::iswspace std::iswlower etc), then you can use boost::wregex to process Unicode. However, there are several disadvantages to this approach:

· It©s not portable: there©s no guarantee on the width of wchar_t, or even whether the runtime treats wide characters as Unicode at all, most Windows compilers do so, but many Unix systems do not.

· There©s no support for Unicode-speci®c character classes: [[:Nd:]], [[:Po:]] etc.

· You can only search strings that are encoded as sequences of wide characters, it is not possible to search UTF-8, or even UTF-16 on many platforms.

Use a Unicode Aware Regular Expression Type.

If you have the ICU library, then Boost.Regex can be con®gured to make use of it, and provide a distinct regular expression type (boost::u32regex), that supports both Unicode speci®c character properties, and the searching of text that is encoded in either UTF- 8, UTF-16, or UTF-32. See: ICU string class support.

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Understanding Marked Sub-Expressions and Captures

Captures are the iterator ranges that are "captured" by marked sub-expressions as a regular expression gets matched. Each marked sub-expression can result in more than one capture, if it is matched more than once. This document explains how captures and marked sub-expressions in Boost.Regex are represented and accessed.

Marked sub-expressions

Every time a Perl regular expression contains a parenthesis group (), it spits out an extra ®eld, known as a marked sub-expression, for example the expression:

(\w+)\W+(\w+)

Has two marked sub-expressions (known as $1 and $2 respectively), in addition the complete match is known as $&, everything before the ®rst match as $Á, and everything after the match as $©. So if the above expression is searched for within "@abc def--", then we obtain:

Sub-expression Text found

$Á "@"

$& "abc def"

$1 "abc"

$2 "def"

$© "--"

In Boost.Regex all these are accessible via the match_results class that gets ®lled in when calling one of the regular expression matching algorithms ( regex_search, regex_match, or regex_iterator). So given:

boost::match_results m;

The Perl and Boost.Regex equivalents are as follows:

Perl Boost.Regex

$Á m.prefix()

$& m[0]

$n m[n]

$© m.suffix()

In Boost.Regex each sub-expression match is represented by a sub_match object, this is basically just a pair of iterators denoting the start and end position of the sub-expression match, but there are some additional operators provided so that objects of type sub_match behave a lot like a std::basic_string: for example they are implicitly convertible to a basic_string, they can be compared to a string, added to a string, or streamed out to an output stream.

Unmatched Sub-Expressions

When a regular expression match is found there is no need for all of the marked sub-expressions to have participated in the match, for example the expression:

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(abc)|(def) can match either $1 or $2, but never both at the same time. In Boost.Regex you can determine which sub-expressions matched by accessing the sub_match::matched data member.

Repeated Captures

When a marked sub-expression is repeated, then the sub-expression gets "captured" multiple times, however normally only the ®nal capture is available, for example if

(?:(\w+)\W+)+ is matched against

one fine day

Then $1 will contain the string "day", and all the previous captures will have been forgotten.

However, Boost.Regex has an experimental feature that allows all the capture information to be retained - this is accessed either via the match_results::captures member function or the sub_match::captures member function. These functions return a container that contains a sequence of all the captures obtained during the regular expression matching. The following example program shows how this information may be used:

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#include #include

void print_captures(const std::string& regx, const std::string& text) { boost::regex e(regx); boost::smatch what; std::cout << "Expression: \"" << regx << "\"\n"; std::cout << "Text: \"" << text << "\"\n"; if(boost::regex_match(text, what, e, boost::match_extra)) { unsigned i, j; std::cout << "** Match found **\n Sub-Expressions:\n"; for(i = 0; i < what.size(); ++i) std::cout << " $" << i << " = \"" << what[i] << "\"\n"; std::cout << " Captures:\n"; for(i = 0; i < what.size(); ++i) { std::cout << " $" << i << " = {"; for(j = 0; j < what.captures(i).size(); ++j) { if(j) std::cout << ", "; else std::cout << " "; std::cout << "\"" << what.captures(i)[j] << "\""; } std::cout << " }\n"; } } else { std::cout << "** No Match found **\n"; } }

int main(int , char* []) { print_captures("(([[:lower:]]+)|([[:upper:]]+))+", "aBBcccDDDDDeeeeeeee"); print_captures("(.*)bar|(.*)bah", "abcbar"); print_captures("(.*)bar|(.*)bah", "abcbah"); print_captures("^(?:(\\w+)|(?>\\W+))*$", "now is the time for all good men to come to the aid of the party"); return 0; }

Which produces the following output:

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Expression: "(([[:lower:]]+)|([[:upper:]]+))+" Text: "aBBcccDDDDDeeeeeeee" ** Match found ** Sub-Expressions: $0 = "aBBcccDDDDDeeeeeeee" $1 = "eeeeeeee" $2 = "eeeeeeee" $3 = "DDDDD" Captures: $0 = { "aBBcccDDDDDeeeeeeee" } $1 = { "a", "BB", "ccc", "DDDDD", "eeeeeeee" } $2 = { "a", "ccc", "eeeeeeee" } $3 = { "BB", "DDDDD" } Expression: "(.*)bar|(.*)bah" Text: "abcbar" ** Match found ** Sub-Expressions: $0 = "abcbar" $1 = "abc" $2 = "" Captures: $0 = { "abcbar" } $1 = { "abc" } $2 = { } Expression: "(.*)bar|(.*)bah" Text: "abcbah" ** Match found ** Sub-Expressions: $0 = "abcbah" $1 = "" $2 = "abc" Captures: $0 = { "abcbah" } $1 = { } $2 = { "abc" } Expression: "^(?:(\w+)|(?>\W+))*$" Text: "now is the time for all good men to come to the aid of the party" ** Match found ** Sub-Expressions: $0 = "now is the time for all good men to come to the aid of the party" $1 = "party" Captures: $0 = { "now is the time for all good men to come to the aid of the party" } $1 = { "now", "is", "the", "time", "for", "all", "good", "men", "to", "come", "to", "the", "aid", "of", "the", "party" }

Unfortunately enabling this feature has an impact on performance (even if you don©t use it), and a much bigger impact if you do use it, therefore to use this feature you need to:

· De®ne BOOST_REGEX_MATCH_EXTRA for all translation units including the library source (the best way to do this is to uncomment this de®ne in boost/regex/user.hpp and then rebuild everything.

· Pass the match_extra ¯ag to the particular algorithms where you actually need the captures information (regex_search, regex_match, or regex_iterator).

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Partial Matches

The match_flag_type match_partial can be passed to the following algorithms: regex_match, regex_search, and regex_grep, and used with the iterator regex_iterator. When used it indicates that partial as well as full matches should be found. A partial match is one that matched one or more characters at the end of the text input, but did not match all of the regular expression (although it may have done so had more input been available). Partial matches are typically used when either validating data input (checking each character as it is entered on the keyboard), or when searching texts that are either too long to load into memory (or even into a memory mapped ®le), or are of indeterminate length (for example the source may be a socket or similar). Partial and full matches can be differentiated as shown in the following table (the variable M represents an instance of match_results as ®lled in by regex_match, regex_search or regex_grep):

Result M[0].matched M[0].®rst M[0].second

No match False Unde®ned Unde®ned Unde®ned

Partial match True False Start of partial match. End of partial match (end of text).

Full match True True Start of full match. End of full match.

Be aware that using partial matches can sometimes result in somewhat imperfect behavior:

· There are some expressions, such as ".*abc" that will always produce a partial match. This problem can be reduced by careful construction of the regular expressions used, or by setting ¯ags like match_not_dot_newline so that expressions like .* can©t match past line boundaries.

· Boost.Regex currently prefers leftmost matches to full matches, so for example matching "abc|b" against "ab" produces a partial match against the "ab" rather than a full match against "b". It©s more ef®cient to work this way, but may not be the behavior you want in all situations.

The following example tests to see whether the text could be a valid credit card number, as the user presses a key, the character entered would be added to the string being built up, and passed to is_possible_card_number. If this returns true then the text could be a valid card number, so the user interface©s OK button would be enabled. If it returns false, then this is not yet a valid card number, but could be with more input, so the user interface would disable the OK button. Finally, if the procedure throws an exception the input could never become a valid number, and the inputted character must be discarded, and a suitable error indication displayed to the user.

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#include #include #include

boost::regex e("(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})");

bool is_possible_card_number(const std::string& input) { // // return false for partial match, true for full match, or throw for // impossible match based on what we have so far... boost::match_results what; if(0 == boost::regex_match(input, what, e, boost::match_default | boost::match_partial)) { // the input so far could not possibly be valid so reject it: throw std::runtime_error( "Invalid data entered - this could not possibly be a valid card number"); } // OK so far so good, but have we finished? if(what[0].matched) { // excellent, we have a result: return true; } // what we have so far is only a partial match... return false; }

In the following example, text input is taken from a stream containing an unknown amount of text; this example simply counts the number of html tags encountered in the stream. The text is loaded into a buffer and searched a part at a time, if a partial match was encountered, then the partial match gets searched a second time as the start of the next batch of text:

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#include #include #include #include #include

// match some kind of html tag: boost::regex e("<[^>]*>"); // count how many: unsigned int tags = 0; void search(std::istream& is) { // buffer we©ll be searching in: char buf[4096]; // saved position of end of partial match: const char* next_pos = buf + sizeof(buf); // flag to indicate whether there is more input to come: bool have_more = true;

while(have_more) { // how much do we copy forward from last try: unsigned leftover = (buf + sizeof(buf)) - next_pos; // and how much is left to fill: unsigned size = next_pos - buf; // copy forward whatever we have left: std::memmove(buf, next_pos, leftover); // fill the rest from the stream: is.read(buf + leftover, size); unsigned read = is.gcount(); // check to see if we©ve run out of text: have_more = read == size; // reset next_pos: next_pos = buf + sizeof(buf); // and then iterate: boost::cregex_iterator a( buf, buf + read + leftover, e, boost::match_default | boost::match_partial); boost::cregex_iterator b;

while(a != b) { if((*a)[0].matched == false) { // Partial match, save position and break: next_pos = (*a)[0].first; break; } else { // full match: ++tags; }

// move to next match: ++a; } } }

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Regular Expression Syntax

This section covers the regular expression syntax used by this library, this is a programmers guide, the actual syntax presented to your program©s users will depend upon the ¯ags used during expression compilation.

There are three main syntax options available, depending upon how you construct the regular expression object:

· Perl (this is the default behavior).

· POSIX extended (including the egrep and awk variations).

· POSIX Basic (including the grep and emacs variations).

You can also construct a regular expression that treats every character as a literal, but that©s not really a "syntax"! Perl Regular Expression Syntax Synopsis

The Perl regular expression syntax is based on that used by the programming language Perl . Perl regular expressions are the default behavior in Boost.Regex or you can pass the ¯ag perl to the basic_regex constructor, for example:

// e1 is a case sensitive Perl regular expression: // since Perl is the default option there©s no need to explicitly specify the syntax used here: boost::regex e1(my_expression); // e2 a case insensitive Perl regular expression: boost::regex e2(my_expression, boost::regex::perl|boost::regex::icase);

Perl Regular Expression Syntax

In Perl regular expressions, all characters match themselves except for the following special characters:

.[{}()\*+?|^$

Wildcard

The single character ©.© when used outside of a character set will match any single character except:

· The NULL character when the ¯ag match_not_dot_null is passed to the matching algorithms.

· The newline character when the ¯ag match_not_dot_newline is passed to the matching algorithms.

Anchors

A ©^© character shall match the start of a line.

A ©$© character shall match the end of a line.

Marked sub-expressions

A section beginning ( and ending ) acts as a marked sub-expression. Whatever matched the sub-expression is split out in a separate ®eld by the matching algorithms. Marked sub-expressions can also repeated, or referred to by a back-reference.

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Non-marking grouping

A marked sub-expression is useful to lexically group part of a regular expression, but has the side-effect of spitting out an extra ®eld in the result. As an alternative you can lexically group part of a regular expression, without generating a marked sub-expression by using (?: and ) , for example (?:ab)+ will repeat ab without splitting out any separate sub-expressions.

Repeats

Any atom (a single character, a marked sub-expression, or a character class) can be repeated with the *, +, ?, and {} operators.

The * operator will match the preceding atom zero or more times, for example the expression a*b will match any of the following:

b ab aaaaaaaab

The + operator will match the preceding atom one or more times, for example the expression a+b will match any of the following:

ab aaaaaaaab

But will not match:

The ? operator will match the preceding atom zero or one times, for example the expression ca?b will match any of the following:

cb cab

But will not match:

caab

An atom can also be repeated with a bounded repeat: a{n} Matches ©a© repeated exactly n times. a{n,} Matches ©a© repeated n or more times. a{n, m} Matches ©a© repeated between n and m times inclusive.

For example:

^a{2,3}$

Will match either of:

aa aaa

But neither of:

a aaaa

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It is an error to use a repeat operator, if the preceding construct can not be repeated, for example:

a(*)

Will raise an error, as there is nothing for the * operator to be applied to.

Non greedy repeats

The normal repeat operators are "greedy", that is to say they will consume as much input as possible. There are non-greedy versions available that will consume as little input as possible while still producing a match.

*? Matches the previous atom zero or more times, while consuming as little input as possible.

+? Matches the previous atom one or more times, while consuming as little input as possible.

?? Matches the previous atom zero or one times, while consuming as little input as possible.

{n,}? Matches the previous atom n or more times, while consuming as little input as possible.

{n,m}? Matches the previous atom between n and m times, while consuming as little input as possible.

Possessive repeats

By default when a repeated pattern does not match then the engine will backtrack until a match is found. However, this behaviour can sometime be undesireable so there are also "possessive" repeats: these match as much as possible and do not then allow backtracking if the rest of the expression fails to match.

*+ Matches the previous atom zero or more times, while giving nothing back.

++ Matches the previous atom one or more times, while giving nothing back.

?+ Matches the previous atom zero or one times, while giving nothing back.

{n,}+ Matches the previous atom n or more times, while giving nothing back.

{n,m}+ Matches the previous atom between n and m times, while giving nothing back.

Back references

An escape character followed by a digit n, where n is in the range 1-9, matches the same string that was matched by sub-expression n. For example the expression:

^(a*).*\1$

Will match the string:

aaabbaaa

But not the string:

aaabba

You can also use the \g escape for the same function, for example:

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Escape Meaning

\g1 Match whatever matched sub-expression 1

\g{1} Match whatever matched sub-expression 1: this form allows for safer parsing of the expression in cases like \g{1}2 or for indexes higher than 9 as in \g{1234}

\g-1 Match whatever matched the last opened sub-expression

\g{-2} Match whatever matched the last but one opened sub-expression

\g{one} Match whatever matched the sub-expression named "one"

Finally the \k escape can be used to refer to named subexpressions, for example \k will match whatever matched the subexpression named "two".

Alternation

The | operator will match either of its arguments, so for example: abc|def will match either "abc" or "def".

Parenthesis can be used to group alternations, for example: ab(d|ef) will match either of "abd" or "abef".

Empty alternatives are not allowed (these are almost always a mistake), but if you really want an empty alternative use (?:) as a placeholder, for example:

|abc is not a valid expression, but

(?:)|abc is and is equivalent, also the expression:

(?:abc)?? has exactly the same effect.

Character sets

A character set is a bracket-expression starting with [ and ending with ], it de®nes a set of characters, and matches any single character that is a member of that set.

A bracket expression may contain any combination of the following:

Single characters

For example [abc], will match any of the characters ©a©, ©b©, or ©c©.

Character ranges

For example [a-c] will match any single character in the range ©a© to ©c©. By default, for Perl regular expressions, a character x is within the range y to z, if the code point of the character lies within the codepoints of the endpoints of the range. Alternatively, if you set the collate ¯ag when constructing the regular expression, then ranges are locale sensitive.

Negation

If the bracket-expression begins with the ^ character, then it matches the complement of the characters it contains, for example [^a-c] matches any character that is not in the range a-c.

Character classes

An expression of the form [[:name:]] matches the named character class "name", for example [[:lower:]] matches any lower case character. See character class names.

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Collating Elements

An expression of the form [[.col.]] matches the collating element col. A collating element is any single character, or any sequence of characters that collates as a single unit. Collating elements may also be used as the end point of a range, for example: [[.ae.]- c] matches the character sequence "ae", plus any single character in the range "ae"-c, assuming that "ae" is treated as a single collating element in the current locale.

As an extension, a collating element may also be speci®ed via it©s symbolic name, for example:

[[.NUL.]] matches a \0 character.

Equivalence classes

An expression of the form [[=col=]], matches any character or collating element whose primary sort key is the same as that for collating element col, as with collating elements the name col may be a symbolic name. A primary sort key is one that ignores case, accentation, or locale-speci®c tailorings; so for example [[=a=]] matches any of the characters: a, À, Á, Â, Ã, Ä, Å, A, à, á, â, ã, ä and å. Unfortunately implementation of this is reliant on the platform©s collation and localisation support; this feature can not be relied upon to work portably across all platforms, or even all locales on one platform.

Escaped Characters

All the escape sequences that match a single character, or a single character class are permitted within a character class de®nition. For example [\[\]] would match either of [ or ] while [\W\d] would match any character that is either a "digit", or is not a "word" character.

Combinations

All of the above can be combined in one character set declaration, for example: [[:digit:]a-c[.NUL.]].

Escapes

Any special character preceded by an escape shall match itself.

The following escape sequences are all synonyms for single characters:

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Escape Character

\a \a

\e 0x1B

\f \f

\r \r

\t \t

\v \v

\b \b (but only inside a character class declaration).

\cX An ASCII escape sequence - the character whose code point is X % 32

\xdd A hexadecimal escape sequence - matches the single character whose code point is 0xdd.

\x{dddd} A hexadecimal escape sequence - matches the single character whose code point is 0xdddd.

\0ddd An octal escape sequence - matches the single character whose code point is 0ddd.

\N{name} Matches the single character which has the symbolic name name. For example \N{newline} matches the single character \n.

"Single character" character classes:

Any escaped character x, if x is the name of a character class shall match any character that is a member of that class, and any escaped character X, if x is the name of a character class, shall match any character not in that class.

The following are supported by default:

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Escape sequence Equivalent to

\d [[:digit:]]

\l [[:lower:]]

\s [[:space:]]

\u [[:upper:]]

\w [[:word:]]

\h Horizontal whitespace

\v Vertical whitespace

\D [^[:digit:]]

\L [^[:lower:]]

\S [^[:space:]]

\U [^[:upper:]]

\W [^[:word:]]

\H Not Horizontal whitespace

\V Not Vertical whitespace

Character Properties

The character property names in the following table are all equivalent to the names used in character classes.

Form Description Equivalent character set form

\pX Matches any character that has the prop- [[:X:]] erty X.

\p{Name} Matches any character that has the prop- [[:Name:]] erty Name.

\PX Matches any character that does not have [^[:X:]] the property X.

\P{Name} Matches any character that does not have [^[:Name:]] the property Name.

For example \pd matches any "digit" character, as does \p{digit}.

Word Boundaries

The following escape sequences match the boundaries of words:

< Matches the start of a word.

> Matches the end of a word.

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\b Matches a word boundary (the start or end of a word).

\B Matches only when not at a word boundary.

Buffer boundaries

The following match only at buffer boundaries: a "buffer" in this context is the whole of the input text that is being matched against (note that ^ and $ may match embedded newlines within the text).

\Á Matches at the start of a buffer only.

\© Matches at the end of a buffer only.

\A Matches at the start of a buffer only (the same as \Á).

\z Matches at the end of a buffer only (the same as \©).

\Z Matches a zero-width assertion consisting of an optional sequence of newlines at the end of a buffer: equivalent to the regular expression (?=\v*\z). Note that this is subtly different from Perl which behaves as if matching (?=\n?\z).

Continuation Escape

The sequence \G matches only at the end of the last match found, or at the start of the text being matched if no previous match was found. This escape useful if you©re iterating over the matches contained within a text, and you want each subsequence match to start where the last one ended.

Quoting escape

The escape sequence \Q begins a "quoted sequence": all the subsequent characters are treated as literals, until either the end of the regular expression or \E is found. For example the expression: \Q*+\Ea+ would match either of:

\*+a \*+aaa

Unicode escapes

\C Matches a single code point: in Boost regex this has exactly the same effect as a "." operator. \X Matches a combining character sequence: that is any non-combining character followed by a sequence of zero or more combining characters.

Matching Line Endings

The escape sequence \R matches any line ending character sequence, speci®cally it is identical to the expression (?>\x0D\x0A?|[\x0A-\x0C\x85\x{2028}\x{2029}]).

Keeping back some text

\K Resets the start location of $0 to the current text position: in other words everything to the left of \K is "kept back" and does not form part of the regular expression match. $Á is updated accordingly.

For example foo\Kbar matched against the text "foobar" would return the match "bar" for $0 and "foo" for $Á. This can be used to simulate variable width lookbehind assertions.

Any other escape

Any other escape sequence matches the character that is escaped, for example \@ matches a literal ©@©.

Perl Extended Patterns

Perl-speci®c extensions to the regular expression syntax all start with (?.

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Named Subexpressions

You can create a named subexpression using:

(?expression)

Which can be then be refered to by the name NAME. Alternatively you can delimit the name using ©NAME© as in:

(?©NAME©expression)

These named subexpressions can be refered to in a backreference using either \g{NAME} or \k and can also be refered to by name in a Perl format string for search and replace operations, or in the match_results member functions.

Comments

(?# ... ) is treated as a comment, it©s contents are ignored.

Modifiers

(?imsx-imsx ... ) alters which of the perl modi®ers are in effect within the pattern, changes take effect from the point that the block is ®rst seen and extend to any enclosing ). Letters before a ©-© turn that perl modi®er on, letters afterward, turn it off.

(?imsx-imsx:pattern) applies the speci®ed modi®ers to pattern only.

Non-marking groups

(?:pattern) lexically groups pattern, without generating an additional sub-expression.

Branch reset

(?|pattern) resets the subexpression count at the start of each "|" alternative within pattern.

The sub-expression count following this construct is that of whichever branch had the largest number of sub-expressions. This construct is useful when you want to capture one of a number of alternative matches in a single sub-expression index.

In the following example the index of each sub-expression is shown below the expression:

# before ------branch-reset------after / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x # 1 2 2 3 2 3 4

Lookahead

(?=pattern) consumes zero characters, only if pattern matches.

(?!pattern) consumes zero characters, only if pattern does not match.

Lookahead is typically used to create the logical AND of two regular expressions, for example if a password must contain a lower case letter, an upper case letter, a punctuation symbol, and be at least 6 characters long, then the expression:

(?=.*[[:lower:]])(?=.*[[:upper:]])(?=.*[[:punct:]]).{6,} could be used to validate the password.

Lookbehind

(?<=pattern) consumes zero characters, only if pattern could be matched against the characters preceding the current position (pattern must be of ®xed length).

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Independent sub-expressions

(?>pattern) pattern is matched independently of the surrounding patterns, the expression will never backtrack into pattern. Inde- pendent sub-expressions are typically used to improve performance; only the best possible match for pattern will be considered, if this doesn©t allow the expression as a whole to match then no match is found at all.

Recursive Expressions

(?N) (?-N) (?+N) (?R) (?0) (?&NAME)

(?R) and (?0) recurse to the start of the entire pattern.

(?N) executes sub-expression N recursively, for example (?2) will recurse to sub-expression 2.

(?-N) and (?+N) are relative recursions, so for example (?-1) recurses to the last sub-expression to be declared, and (?+1) recurses to the next sub-expression to be declared.

(?&NAME) recurses to named sub-expression NAME.

Conditional Expressions

(?(condition)yes-pattern|no-pattern) attempts to match yes-pattern if the condition is true, otherwise attempts to match no-pattern.

(?(condition)yes-pattern) attempts to match yes-pattern if the condition is true, otherwise matches the NULL string. condition may be either: a forward lookahead assert, the index of a marked sub-expression (the condition becomes true if the sub- expression has been matched), or an index of a recursion (the condition become true if we are executing directly inside the speci®ed recursion).

Here is a summary of the possible predicates:

· (?(?=assert)yes-pattern|no-pattern) Executes yes-pattern if the forward look-ahead assert matches, otherwise executes no-pattern.

· (?(?!assert)yes-pattern|no-pattern) Executes yes-pattern if the forward look-ahead assert does not match, otherwise executes no-pattern.

· (?(N)yes-pattern|no-pattern) Executes yes-pattern if subexpression N has been matched, otherwise executes no-pattern.

· (?()yes-pattern|no-pattern) Executes yes-pattern if named subexpression name has been matched, otherwise executes no-pattern.

· (?(©name©)yes-pattern|no-pattern) Executes yes-pattern if named subexpression name has been matched, otherwise executes no-pattern.

· (?(R)yes-pattern|no-pattern) Executes yes-pattern if we are executing inside a recursion, otherwise executes no-pattern.

· (?(RN)yes-pattern|no-pattern) Executes yes-pattern if we are executing inside a recursion to sub-expression N, otherwise executes no-pattern.

· (?(R&name)yes-pattern|no-pattern) Executes yes-pattern if we are executing inside a recursion to named sub-expression name, otherwise executes no-pattern.

· (?(DEFINE)never-exectuted-pattern) De®nes a block of code that is never executed and matches no characters: this is usually used to de®ne one or more named sub-expressions which are refered to from elsewhere in the pattern.

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Operator precedence

The order of precedence for of operators is as follows:

1. Collation-related bracket symbols [==] [::] [..]

2. Escaped characters [^]

3. Character set (bracket expression) []

4. Grouping ()

5. Single-character-ERE duplication * + ? {m,n}

6. Concatenation

7. Anchoring ^$

8. Alternation | What gets matched

If you view the regular expression as a directed (possibly cyclic) graph, then the best match found is the ®rst match found by a depth- ®rst-search performed on that graph, while matching the input text.

Alternatively:

The best match found is the leftmost match, with individual elements matched as follows;

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Construct What gets matched

AtomA AtomB Locates the best match for AtomA that has a following match for AtomB.

Expression1 | Expression2 If Expresion1 can be matched then returns that match, otherwise attempts to match Expression2.

S{N} Matches S repeated exactly N times.

S{N,M} Matches S repeated between N and M times, and as many times as possible.

S{N,M}? Matches S repeated between N and M times, and as few times as possible.

S?, S*, S+ The same as S{0,1}, S{0,UINT_MAX}, S{1,UINT_MAX} respectively.

S??, S*?, S+? The same as S{0,1}?, S{0,UINT_MAX}?, S{1,UINT_MAX}? respectively.

(?>S) Matches the best match for S, and only that.

(?=S), (?<=S) Matches only the best match for S (this is only visible if there are capturing parenthesis within S).

(?!S), (?

(?(condition)yes-pattern | no-pattern) If condition is true, then only yes-pattern is considered, otherwise only no-pattern is considered.

Variations

The options normal, ECMAScript, JavaScript and JScript are all synonyms for perl. Options

There are a variety of ¯ags that may be combined with the perl option when constructing the regular expression, in particular note that the newline_alt option alters the syntax, while the collate, nosubs and icase options modify how the case and locale sensitivity are to be applied. Pattern Modifiers

The perl smix modi®ers can either be applied using a (?smix-smix) pre®x to the regular expression, or with one of the regex- compile time ¯ags no_mod_m, mod_x, mod_s, and no_mod_s. References

Perl 5.8.

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POSIX Extended Regular Expression Syntax Synopsis

The POSIX-Extended regular expression syntax is supported by the POSIX C regular expression API©s, and variations are used by the utilities egrep and awk. You can construct POSIX extended regular expressions in Boost.Regex by passing the ¯ag extended to the regex constructor, for example:

// e1 is a case sensitive POSIX-Extended expression: boost::regex e1(my_expression, boost::regex::extended); // e2 a case insensitive POSIX-Extended expression: boost::regex e2(my_expression, boost::regex::extended|boost::regex::icase);

POSIX Extended Syntax

In POSIX-Extended regular expressions, all characters match themselves except for the following special characters:

.[{}()\*+?|^$

Wildcard:

The single character ©.© when used outside of a character set will match any single character except:

· The NULL character when the ¯ag match_no_dot_null is passed to the matching algorithms.

· The newline character when the ¯ag match_not_dot_newline is passed to the matching algorithms.

Anchors:

A ©^© character shall match the start of a line when used as the ®rst character of an expression, or the ®rst character of a sub-expression.

A ©$© character shall match the end of a line when used as the last character of an expression, or the last character of a sub-expression.

Marked sub-expressions:

Repeats:

Any atom (a single character, a marked sub-expression, or a character class) can be repeated with the *, +, ?, and {} operators.

The * operator will match the preceding atom zero or more times, for example the expression a*b will match any of the following:

b ab aaaaaaaab

The + operator will match the preceding atom one or more times, for example the expression a+b will match any of the following:

ab aaaaaaaab

But will not match:

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The ? operator will match the preceding atom zero or one times, for example the expression ca?b will match any of the following:

cb cab

But will not match:

caab

For example:

^a{2,3}$

Will match either of:

aa aaa

But neither of:

a aaaa

It is an error to use a repeat operator, if the preceding construct can not be repeated, for example:

a(*)

Will raise an error, as there is nothing for the * operator to be applied to.

Back references:

An escape character followed by a digit n, where n is in the range 1-9, matches the same string that was matched by sub-expression n. For example the expression:

^(a*).*\1$

Will match the string:

aaabbaaa

But not the string:

aaabba

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Caution

The POSIX standard does not support back-references for "extended" regular expressions, this is a compatible extension to that standard.

Alternation

The | operator will match either of its arguments, so for example: abc|def will match either "abc" or "def".

Parenthesis can be used to group alternations, for example: ab(d|ef) will match either of "abd" or "abef".

Character sets:

A character set is a bracket-expression starting with [ and ending with ], it de®nes a set of characters, and matches any single character that is a member of that set.

A bracket expression may contain any combination of the following:

Single characters:

For example [abc], will match any of the characters ©a©, ©b©, or ©c©.

Character ranges:

For example [a-c] will match any single character in the range ©a© to ©c©. By default, for POSIX-Extended regular expressions, a character x is within the range y to z, if it collates within that range; this results in locale speci®c behavior . This behavior can be turned off by unsetting the collate option ¯ag - in which case whether a character appears within a range is determined by comparing the code points of the characters only.

Negation:

If the bracket-expression begins with the ^ character, then it matches the complement of the characters it contains, for example [^a-c] matches any character that is not in the range a-c.

Character classes:

An expression of the form [[:name:]] matches the named character class "name", for example [[:lower:]] matches any lower case character. See character class names.

Collating Elements:

An expression of the form [[.col.] matches the collating element col. A collating element is any single character, or any sequence of characters that collates as a single unit. Collating elements may also be used as the end point of a range, for example: [[.ae.]-c] matches the character sequence "ae", plus any single character in the range "ae"-c, assuming that "ae" is treated as a single collating element in the current locale.

Collating elements may be used in place of escapes (which are not normally allowed inside character sets), for example [[.^.]abc] would match either one of the characters ©abc^©.

As an extension, a collating element may also be speci®ed via its symbolic name, for example:

[[.NUL.]] matches a NUL character.

Equivalence classes:

An expression of the form [[=col=]], matches any character or collating element whose primary sort key is the same as that for collating element col, as with colating elements the name col may be a symbolic name. A primary sort key is one that ignores case,

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Combinations:

All of the above can be combined in one character set declaration, for example: [[:digit:]a-c[.NUL.]].

Escapes

The POSIX standard de®nes no escape sequences for POSIX-Extended regular expressions, except that:

· Any special character preceded by an escape shall match itself.

· The effect of any ordinary character being preceded by an escape is unde®ned.

· An escape inside a character class declaration shall match itself: in other words the escape character is not "special" inside a character class declaration; so [\^] will match either a literal ©\© or a ©^©.

However, that©s rather restrictive, so the following standard-compatible extensions are also supported by Boost.Regex:

Escapes matching a specific character

The following escape sequences are all synonyms for single characters:

Escape Character

\a ©\a©

\e 0x1B

\f \f

\n \n

\r \r

\t \t

\v \v

\b \b (but only inside a character class declaration).

\cX An ASCII escape sequence - the character whose code point is X % 32

\xdd A hexadecimal escape sequence - matches the single character whose code point is 0xdd.

\x{dddd} A hexadecimal escape sequence - matches the single character whose code point is 0xdddd.

\0ddd An octal escape sequence - matches the single character whose code point is 0ddd.

\N{Name} Matches the single character which has the symbolic name name. For example \\N{newline} matches the single character \n.

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"Single character" character classes:

The following are supported by default:

Escape sequence Equivalent to

\d [[:digit:]]

\l [[:lower:]]

\s [[:space:]]

\u [[:upper:]]

\w [[:word:]]

\D [^[:digit:]]

\L [^[:lower:]]

\S [^[:space:]]

\U [^[:upper:]]

\W [^[:word:]]

Character Properties

The character property names in the following table are all equivalent to the names used in character classes.

Form Description Equivalent character set form

\pX Matches any character that has the prop- [[:X:]] erty X.

\p{Name} Matches any character that has the prop- [[:Name:]] erty Name.

\PX Matches any character that does not have [^[:X:]] the property X.

\P{Name} Matches any character that does not have [^[:Name:]] the property Name.

For example \pd matches any "digit" character, as does \p{digit}.

Word Boundaries

The following escape sequences match the boundaries of words:

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Escape Meaning

\< Matches the start of a word.

\> Matches the end of a word.

\b Matches a word boundary (the start or end of a word).

\B Matches only when not at a word boundary.

Buffer boundaries

The following match only at buffer boundaries: a "buffer" in this context is the whole of the input text that is being matched against (note that ^ and $ may match embedded newlines within the text).

Escape Meaning

\Á Matches at the start of a buffer only.

\© Matches at the end of a buffer only.

\A Matches at the start of a buffer only (the same as \Á).

\z Matches at the end of a buffer only (the same as \©).

\Z Matches an optional sequence of newlines at the end of a buffer: equivalent to the regular expression \n*\z

Continuation Escape

Quoting escape

\*+a \*+aaa

Unicode escapes

Escape Meaning

\C Matches a single code point: in Boost regex this has exactly the same effect as a "." operator.

\X Matches a combining character sequence: that is any non-combining character followed by a sequence of zero or more combining characters.

Any other escape

Any other escape sequence matches the character that is escaped, for example \@ matches a literal ©@©.

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Operator precedence

The order of precedence for of operators is as follows:

1. Collation-related bracket symbols [==] [::] [..]

2. Escaped characters \

3. Character set (bracket expression) []

4. Grouping ()

5. Single-character-ERE duplication * + ? {m,n}

6. Concatenation

7. Anchoring ^$

8. Alternation |

What Gets Matched

When there is more that one way to match a regular expression, the "best" possible match is obtained using the leftmost-longest rule. Variations

Egrep

When an expression is compiled with the ¯ag egrep set, then the expression is treated as a newline separated list of POSIX-Extended expressions, a match is found if any of the expressions in the list match, for example:

boost::regex e("abc\ndef", boost::regex::egrep); will match either of the POSIX-Basic expressions "abc" or "def".

As its name suggests, this behavior is consistent with the Unix utility egrep, and with grep when used with the -E option. awk

In addition to the POSIX-Extended features the escape character is special inside a character class declaration.

In addition, some escape sequences that are not de®ned as part of POSIX-Extended speci®cation are required to be supported - however Boost.Regex supports these by default anyway. Options

There are a variety of ¯ags that may be combined with the extended and egrep options when constructing the regular expression, in particular note that the newline_alt option alters the syntax, while the collate, nosubs and icase options modify how the case and locale sensitivity are to be applied. References

IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base De®nitions and Headers, Section 9, Regular Expressions.

IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and Utilities, Section 4, Utilities, egrep.

IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and Utilities, Section 4, Utilities, awk.

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POSIX Basic Regular Expression Syntax Synopsis

The POSIX-Basic regular expression syntax is used by the Unix utility sed, and variations are used by grep and emacs. You can construct POSIX basic regular expressions in Boost.Regex by passing the ¯ag basic to the regex constructor (see syntax_op- tion_type), for example:

// e1 is a case sensitive POSIX-Basic expression: boost::regex e1(my_expression, boost::regex::basic); // e2 a case insensitive POSIX-Basic expression: boost::regex e2(my_expression, boost::regex::basic|boost::regex::icase);

POSIX Basic Syntax

In POSIX-Basic regular expressions, all characters are match themselves except for the following special characters:

.[\*^$

Wildcard:

The single character ©.© when used outside of a character set will match any single character except:

· The NULL character when the ¯ag match_no_dot_null is passed to the matching algorithms.

· The newline character when the ¯ag match_not_dot_newline is passed to the matching algorithms.

Anchors:

A ©^© character shall match the start of a line when used as the ®rst character of an expression, or the ®rst character of a sub-expression.

A ©$© character shall match the end of a line when used as the last character of an expression, or the last character of a sub-expression.

Marked sub-expressions:

A section beginning $ and ending $ acts as a marked sub-expression. Whatever matched the sub-expression is split out in a separate ®eld by the matching algorithms. Marked sub-expressions can also repeated, or referred-to by a back-reference.

Repeats:

Any atom (a single character, a marked sub-expression, or a character class) can be repeated with the * operator.

For example a* will match any number of letter a©s repeated zero or more times (an atom repeated zero times matches an empty string), so the expression a*b will match any of the following:

b ab aaaaaaaab

An atom can also be repeated with a bounded repeat: a\{n\} Matches ©a© repeated exactly n times. a\{n,\} Matches ©a© repeated n or more times. a\{n, m\} Matches ©a© repeated between n and m times inclusive.

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For example:

^a{2,3}$

Will match either of:

aa aaa

But neither of:

a aaaa

It is an error to use a repeat operator, if the preceding construct can not be repeated, for example:

a(*)

Will raise an error, as there is nothing for the * operator to be applied to.

Back references:

An escape character followed by a digit n, where n is in the range 1-9, matches the same string that was matched by sub-expression n. For example the expression:

^$a*$.*\1$

Will match the string:

aaabbaaa

But not the string:

aaabba

Character sets:

A character set is a bracket-expression starting with [ and ending with ], it de®nes a set of characters, and matches any single character that is a member of that set.

A bracket expression may contain any combination of the following:

Single characters:

For example [abc], will match any of the characters ©a©, ©b©, or ©c©.

Character ranges:

For example [a-c] will match any single character in the range ©a© to ©c©. By default, for POSIX-Basic regular expressions, a character x is within the range y to z, if it collates within that range; this results in locale speci®c behavior. This behavior can be turned off by unsetting the collate option ¯ag when constructing the regular expression - in which case whether a character appears within a range is determined by comparing the code points of the characters only.

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Negation:

If the bracket-expression begins with the ^ character, then it matches the complement of the characters it contains, for example [^a-c] matches any character that is not in the range a-c.

Character classes:

An expression of the form [[:name:]] matches the named character class "name", for example [[:lower:]] matches any lower case character. See character class names.

Collating Elements:

An expression of the form [[.col.] matches the collating element col. A collating element is any single character, or any sequence of characters that collates as a single unit. Collating elements may also be used as the end point of a range, for example: [[.ae.]-c] matches the character sequence "ae", plus any single character in the rangle "ae"-c, assuming that "ae" is treated as a single collating element in the current locale.

Collating elements may be used in place of escapes (which are not normally allowed inside character sets), for example [[.^.]abc] would match either one of the characters ©abc^©.

As an extension, a collating element may also be speci®ed via its symbolic name, for example:

[[.NUL.]] matches a ©NUL© character. See collating element names.

Equivalence classes:

An expression of theform [[=col=]], matches any character or collating element whose primary sort key is the same as that for collating element col, as with collating elements the name col may be a collating symbolic name. A primary sort key is one that ignores case, accentation, or locale-speci®c tailorings; so for example [[=a=]] matches any of the characters: a, À, Á, Â, Ã, Ä, Å, A, à, á, â, ã, ä and å. Unfortunately implementation of this is reliant on the platform©s collation and localisation support; this feature can not be relied upon to work portably across all platforms, or even all locales on one platform.

Combinations:

All of the above can be combined in one character set declaration, for example: [[:digit:]a-c[.NUL.]].

Escapes

With the exception of the escape sequences \{, \}, $, and $, which are documented above, an escape followed by any character matches that character. This can be used to make the special characters

.[\*^$

"ordinary". Note that the escape character loses its special meaning inside a character set, so [\^] will match either a literal ©\© or a ©^©. What Gets Matched

When there is more that one way to match a regular expression, the "best" possible match is obtained using the leftmost-longest rule. Variations

Grep

When an expression is compiled with the ¯ag grep set, then the expression is treated as a newline separated list of POSIX-Basic expressions, a match is found if any of the expressions in the list match, for example:

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boost::regex e("abc\ndef", boost::regex::grep); will match either of the POSIX-Basic expressions "abc" or "def".

As its name suggests, this behavior is consistent with the Unix utility grep. emacs

In addition to the POSIX-Basic features the following characters are also special:

Character Description

+ repeats the preceding atom one or more times.

? repeats the preceding atom zero or one times.

*? A non-greedy version of *.

+? A non-greedy version of +.

?? A non-greedy version of ?.

And the following escape sequences are also recognised:

Escape Description

\| speci®es an alternative.

\(?: ... ) is a non-marking grouping construct - allows you to lexically group something without spitting out an extra sub-expression.

\w matches any word character.

\W matches any non-word character.

\sx matches any character in the syntax group x, the following emacs groupings are supported: ©s©, © ©, ©_©, ©w©, ©.©, ©)©, ©(©, ©"©, ©\©©, ©>© and ©<©. Refer to the emacs docs for details.

\Sx matches any character not in the syntax grouping x.

\c and \C These are not supported.

\Á matches zero characters only at the start of a buffer (or string being matched).

\© matches zero characters only at the end of a buffer (or string being matched).

\b matches zero characters at a word boundary.

\B matches zero characters, not at a word boundary.

\< matches zero characters only at the start of a word.

\> matches zero characters only at the end of a word.

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Finally, you should note that emacs style regular expressions are matched according to the Perl "depth ®rst search" rules. Emacs expressions are matched this way because they contain Perl-like extensions, that do not interact well with the POSIX-style leftmost- longest rule. Options

There are a variety of ¯ags that may be combined with the basic and grep options when constructing the regular expression, in particular note that the newline_alt, no_char_classes, no-intervals, bk_plus_qm and bk_plus_vbar options all alter the syntax, while the collate and icase options modify how the case and locale sensitivity are to be applied. References

IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base De®nitions and Headers, Section 9, Regular Expressions (FWD.1).

IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and Utilities, Section 4, Utilities, grep (FWD.1).

Emacs Version 21.3. Character Class Names Character Classes that are Always Supported

The following character class names are always supported by Boost.Regex:

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Name POSIX-standard name Description

alnum Yes Any alpha-numeric character.

alpha Yes Any alphabetic character.

blank Yes Any whitespace character that is not a line separator.

cntrl Yes Any control character.

d No Any decimal digit

digit Yes Any decimal digit.

graph Yes Any graphical character.

l No Any lower case character.

lower Yes Any lower case character.

print Yes Any printable character.

punct Yes Any punctuation character.

s No Any whitespace character.

space Yes Any whitespace character.

unicode No Any extended character whose code point is above 255 in value.

u No Any upper case character.

upper Yes Any upper case character.

w No Any word character (alphanumeric characters plus the underscore).

word No Any word character (alphanumeric characters plus the underscore).

xdigit Yes Any hexadecimal digit character.

Character classes that are supported by Unicode Regular Expressions

The following character classes are only supported by Unicode Regular Expressions: that is those that use the u32regex type. The names used are the same as those from Chapter 4 of the Unicode standard.

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Short Name Long Name

ASCII

Any

Assigned

C* Other

Cc Control

Cf Format

Cn Not Assigned

Co Private Use

Cs Surrogate

L* Letter

Ll Lowercase Letter

Lm Modi®er Letter

Lo Other Letter

Lt Titlecase

Lu Uppercase Letter

M* Mark

Mc Spacing Combining Mark

Me Enclosing Mark

Mn Non-Spacing Mark

N* Number

Nd Decimal Digit Number

Nl Letter Number

No Other Number

P* Punctuation

Pc Connector Punctuation

Pd Dash Punctuation

Pe Close Punctuation

Pf Final Punctuation

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Short Name Long Name

Pi Initial Punctuation

Po Other Punctuation

Ps Open Punctuation

S* Symbol

Sc Currency Symbol

Sk Modi®er Symbol

Sm Math Symbol

So Other Symbol

Z* Separator

Zl Line Separator

Zp Paragraph Separator

Zs Space Separator

Collating Names Digraphs

The following are treated as valid digraphs when used as a collating name:

"ae", "Ae", "AE", "ch", "Ch", "CH", "ll", "Ll", "LL", "ss", "Ss", "SS", "nj", "Nj", "NJ", "dz", "Dz", "DZ", "lj", "Lj", "LJ".

So for example the expression:

[[.ae.]-c] ↵ will match any character that collates between the digraph "ae" and the character "c". POSIX Symbolic Names

The following symbolic names are recognised as valid collating element names, in addition to any single character, this allows you to write for example:

[[.left-square-bracket.][.right-square-bracket.]] if you wanted to match either "[" or "]".

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Name Character

NUL \x00

SOH \x01

STX \x02

ETX \x03

EOT \x04

ENQ \x05

ACK \x06 alert \x07 backspace \x08 tab \t newline \n vertical-tab \v form-feed \f carriage-return \r

SO \xE

SI \xF

DLE \x10

DC1 \x11

DC2 \x12

DC3 \x13

DC4 \x14

NAK \x15

SYN \x16

ETB \x17

CAN \x18

EM \x19

SUB \x1A

ESC \x1B

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Name Character

IS4 \x1C

IS3 \x1D

IS2 \x1E

IS1 \x1F space \x20 exclamation-mark ! quotation-mark " number-sign # dollar-sign $ percent-sign % ampersand & apostrophe © left-parenthesis ( right-parenthesis ) asterisk * plus-sign + comma , hyphen - period . slash / zero 0 one 1 two 2 three 3 four 4

®ve 5 six 6 seven 7

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Name Character

eight 8

nine 9

colon :

semicolon ;

less-than-sign <

equals-sign =

greater-than-sign >

question-mark ?

commercial-at @

left-square-bracket [

backslash \

right-square-bracket ]

circum¯ex ~

underscore _

grave-accent Á

left-curly-bracket {

vertical-line |

right-curly-bracket }

tilde ~

DEL \x7F

Named Unicode Characters

When using Unicode aware regular expressions (with the u32regex type), all the normal symbolic names for Unicode characters (those given in Unidata.txt) are recognised. So for example:

[[.CYRILLIC CAPITAL LETTER I.]] ↵ would match the Unicode character 0x0418. The Leftmost Longest Rule

Often there is more than one way of matching a regular expression at a particular location, for POSIX basic and extended regular expressions, the "best" match is determined as follows:

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1. Find the leftmost match, if there is only one match possible at this location then return it.

2. Find the longest of the possible matches, along with any ties. If there is only one such possible match then return it.

3. If there are no marked sub-expressions, then all the remaining alternatives are indistinguishable; return the ®rst of these found.

4. Find the match which has matched the ®rst sub-expression in the leftmost position, along with any ties. If there is only on such match possible then return it.

5. Find the match which has the longest match for the ®rst sub-expression, along with any ties. If there is only one such match then return it.

6. Repeat steps 4 and 5 for each additional marked sub-expression.

7. If there is still more than one possible match remaining, then they are indistinguishable; return the ®rst one found.

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Search and Replace Format String Syntax

Format strings are used by the algorithm regex_replace and by match_results<>::format, and are used to transform one string into another.

There are three kind of format string: Sed, Perl and Boost-Extended.

Alternatively, when the ¯ag format_literal is passed to one of these functions, then the format string is treated as a string literal, and is copied unchanged to the output. Sed Format String Syntax

Sed-style format strings treat all characters as literals except:

character description

& The ampersand character is replaced in the output stream by the the whole of what matched the regular expression. Use \& to output a literal ©&© character.

\ Speci®es an escape sequence.

An escape character followed by any character x, outputs that character unless x is one of the escape sequences shown below.

Escape Meaning

\a Outputs the bell character: ©\a©.

\e Outputs the ANSI escape character (code point 27).

\f Outputs a form feed character: ©\f©

\n Outputs a newline character: ©\n©.

\r Outputs a carriage return character: ©\r©.

\t Outputs a tab character: ©\t©.

\v Outputs a vertical tab character: ©\v©.

\xDD Outputs the character whose hexadecimal code point is 0xDD

\x{DDDD} Outputs the character whose hexadecimal code point is 0xD- DDDD

\cX Outputs the ANSI escape sequence "escape-X".

\D If D is a decimal digit in the range 1-9, then outputs the text that matched sub-expression D.

Perl Format String Syntax

Perl-style format strings treat all characters as literals except ©$© and ©\© which start placeholder and escape sequences respectively.

Placeholder sequences specify that some part of what matched the regular expression should be sent to output as follows:

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Placeholder Meaning

$& Outputs what matched the whole expression.

$MATCH As $&

${^MATCH} As $&

$Á Outputs the text between the end of the last match found (or the start of the text if no previous match was found), and the start of the current match.

$PREMATCH As $Á

${^PREMATCH} As $Á

$© Outputs all the text following the end of the current match.

$POSTMATCH As $©

${^POSTMATCH} As $©

$+ Outputs what matched the last marked sub-expression in the regular expression.

$LAST_PAREN_MATCH As $+

$LAST_SUBMATCH_RESULT Outputs what matched the last sub-expression to be actually matched.

$^N As $LAST_SUBMATCH_RESULT

$$ Outputs a literal ©$©

$n Outputs what matched the n©th sub-expression.

${n} Outputs what matched the n©th sub-expression.

$+{NAME} Outputs whatever matched the sub-expression named "NAME".

Any $-placeholder sequence not listed above, results in ©$© being treated as a literal.

An escape character followed by any character x, outputs that character unless x is one of the escape sequences shown below.

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Escape Meaning

\a Outputs the bell character: ©\a©.

\e Outputs the ANSI escape character (code point 27).

\f Outputs a form feed character: ©\f©

\n Outputs a newline character: ©\n©.

\r Outputs a carriage return character: ©\r©.

\t Outputs a tab character: ©\t©.

\v Outputs a vertical tab character: ©\v©.

\xDD Outputs the character whose hexadecimal code point is 0xDD

\x{DDDD} Outputs the character whose hexadecimal code point is 0xD- DDDD

\cX Outputs the ANSI escape sequence "escape-X".

\D If D is a decimal digit in the range 1-9, then outputs the text that matched sub-expression D.

\l Causes the next character to be outputted, to be output in lower case.

\u Causes the next character to be outputted, to be output in upper case.

\L Causes all subsequent characters to be output in lower case, until a \E is found.

\U Causes all subsequent characters to be output in upper case, until a \E is found.

\E Terminates a \L or \U sequence.

Boost-Extended Format String Syntax

Boost-Extended format strings treat all characters as literals except for ©$©, ©\©, ©(©, ©)©, ©?©, and ©:©.

Grouping

The characters ©(© and ©)© perform lexical grouping, so use $ and $ if you want a to output literal parenthesis.

Conditionals

The character ©?© begins a conditional expression, the general form is:

?Ntrue-expression:false-expression where N is decimal digit.

If sub-expression N was matched, then true-expression is evaluated and sent to output, otherwise false-expression is evaluated and sent to output.

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You will normally need to surround a conditional-expression with parenthesis in order to prevent ambiguities.

For example, the format string "(?1foo:bar)" will replace each match found with "foo" if the sub-expression $1 was matched, and with "bar" otherwise.

For sub-expressions with an index greater than 9, or for access to named sub-expressions use:

?{INDEX}true-expression:false-expression or

?{NAME}true-expression:false-expression

Placeholder Sequences

Placeholder sequences specify that some part of what matched the regular expression should be sent to output as follows:

Placeholder Meaning

$& Outputs what matched the whole expression.

$MATCH As $&

${^MATCH} As $&

$Á Outputs the text between the end of the last match found (or the start of the text if no previous match was found), and the start of the current match.

$PREMATCH As $Á

${^PREMATCH} As $Á

$© Outputs all the text following the end of the current match.

$POSTMATCH As $©

${^POSTMATCH} As $©

$+ Outputs what matched the last marked sub-expression in the regular expression.

$LAST_PAREN_MATCH As $+

$LAST_SUBMATCH_RESULT Outputs what matched the last sub-expression to be actually matched.

$^N As $LAST_SUBMATCH_RESULT

$$ Outputs a literal ©$©

$n Outputs what matched the n©th sub-expression.

${n} Outputs what matched the n©th sub-expression.

$+{NAME} Outputs whatever matched the sub-expression named "NAME".

Any $-placeholder sequence not listed above, results in ©$© being treated as a literal.

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Escape Sequences

An escape character followed by any character x, outputs that character unless x is one of the escape sequences shown below.

Escape Meaning

\a Outputs the bell character: ©\a©.

\e Outputs the ANSI escape character (code point 27).

\f Outputs a form feed character: ©\f©

\n Outputs a newline character: ©\n©.

\r Outputs a carriage return character: ©\r©.

\t Outputs a tab character: ©\t©.

\v Outputs a vertical tab character: ©\v©.

\xDD Outputs the character whose hexadecimal code point is 0xDD

\x{DDDD} Outputs the character whose hexadecimal code point is 0xD- DDDD

\cX Outputs the ANSI escape sequence "escape-X".

\D If D is a decimal digit in the range 1-9, then outputs the text that matched sub-expression D.

\l Causes the next character to be outputted, to be output in lower case.

\u Causes the next character to be outputted, to be output in upper case.

\L Causes all subsequent characters to be output in lower case, until a \E is found.

\U Causes all subsequent characters to be output in upper case, until a \E is found.

\E Terminates a \L or \U sequence.

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Reference basic_regex

Synopsis

#include

The template class basic_regex encapsulates regular expression parsing and compilation. The class takes two template parameters:

· charT: determines the character type, i.e. either char or wchar_t; see charT concept.

· traits: determines the behavior of the character type, for example which character class names are recognized. A default traits class is provided: regex_traits. See also traits concept.

For ease of use there are two typedefs that de®ne the two standard basic_regex instances, unless you want to use custom traits classes or non-standard character types (for example see unicode support), you won©t need to use anything other than these:

namespace boost{

template > class basic_regex;

typedef basic_regex regex; typedef basic_regex wregex;

}

The de®nition of basic_regex follows: it is based very closely on class basic_string, and ful®ls the requirements for a constant- container of charT.

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namespace boost{ template > class basic_regex { public: // types: typedef charT value_type; typedef implementation-specific const_iterator; typedef const_iterator iterator; typedef charT& reference; typedef const charT& const_reference; typedef std::ptrdiff_t difference_type; typedef std::size_t size_type; typedef regex_constants:: syntax_option_type flag_type; typedef typename traits::locale_type locale_type;

// constants: // main option selection: static const regex_constants:: syntax_option_type normal = regex_constants::normal; static const regex_constants:: syntax_option_type ECMAScript = normal; static const regex_constants:: syntax_option_type JavaScript = normal; static const regex_constants:: syntax_option_type JScript = normal; static const regex_constants:: syntax_option_type basic = regex_constants::basic; static const regex_constants:: syntax_option_type extended = regex_constants::extended; static const regex_constants:: syntax_option_type awk = regex_constants::awk; static const regex_constants:: syntax_option_type grep = regex_constants::grep; static const regex_constants:: syntax_option_type egrep = regex_constants::egrep; static const regex_constants:: syntax_option_type sed = basic = regex_constants::sed; static const regex_constants:: syntax_option_type perl = regex_constants::perl; static const regex_constants:: syntax_option_type literal = regex_constants::literal;

// modifiers specific to perl expressions: static const regex_constants:: syntax_option_type no_mod_m = regex_constants::no_mod_m; static const regex_constants:: syntax_option_type no_mod_s = regex_constants::no_mod_s; static const regex_constants:: syntax_option_type mod_s = regex_constants::mod_s; static const regex_constants:: syntax_option_type mod_x = regex_constants::mod_x;

// modifiers specific to POSIX basic expressions: static const regex_constants:: syntax_option_type bk_plus_qm = regex_constants::bk_plus_qm; static const regex_constants:: syntax_option_type bk_vbar = regex_constants::bk_vbar static const regex_constants:: syntax_option_type no_char_classes = regex_constants::no_char_classes static const regex_constants:: syntax_option_type no_intervals = regex_constants::no_intervals

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// common modifiers: static const regex_constants:: syntax_option_type nosubs = regex_constants::nosubs; static const regex_constants:: syntax_option_type optimize = regex_constants::optimize; static const regex_constants:: syntax_option_type collate = regex_constants::collate; static const regex_constants:: syntax_option_type newline_alt = regex_constants::newline_alt; static const regex_constants:: syntax_option_type no_except = regex_constants::newline_alt;

// construct/copy/destroy: explicit basic_regex (); explicit basic_regex(const charT* p, flag_type f = regex_constants::normal); basic_regex(const charT* p1, const charT* p2, flag_type f = regex_constants::normal); basic_regex(const charT* p, size_type len, flag_type f); basic_regex(const basic_regex&); template explicit basic_regex(const basic_string& p, flag_type f = regex_constants::normal); template basic_regex(InputIterator first, InputIterator last, flag_type f = regex_constants::normal);

~basic_regex(); basic_regex& operator=(const basic_regex&); basic_regex& operator= (const charT* ptr); template basic_regex& operator= (const basic_string& p); // iterators: std::pair subexpression(size_type n) const; const_iterator begin() const; const_iterator end() const; // capacity: size_type size() const; size_type max_size() const; bool empty() const; size_type mark_count()const; // // modifiers: basic_regex& assign(const basic_regex& that); basic_regex& assign(const charT* ptr, flag_type f = regex_constants::normal); basic_regex& assign(const charT* ptr, unsigned int len, flag_type f); template basic_regex& assign(const basic_string& s, flag_type f = regex_constants::normal); template basic_regex& assign(InputIterator first, InputIterator last, flag_type f = regex_constants::normal);

// const operations: flag_type flags() const; int status()const; basic_string str() const; int compare(basic_regex&) const;

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// locale: locale_type imbue(locale_type loc); locale_type getloc() const; // swap void swap(basic_regex&) throw(); };

template bool operator == (const basic_regex& lhs, const basic_regex& rhs);

template bool operator != (const basic_regex& lhs, const basic_regex& rhs);

template bool operator < (const basic_regex& lhs, const basic_regex& rhs);

template bool operator <= (const basic_regex& lhs, const basic_regex& rhs);

template bool operator >= (const basic_regex& lhs, const basic_regex& rhs);

template bool operator > (const basic_regex& lhs, const basic_regex& rhs);

template basic_ostream& operator << (basic_ostream& os, const basic_regex& e);

template void swap(basic_regex& e1, basic_regex& e2);

typedef basic_regex regex; typedef basic_regex wregex;

} // namespace boost

Description

Class basic_regex has the following public members:

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// main option selection: static const regex_constants:: syntax_option_type normal = regex_constants::normal; static const regex_constants:: syntax_option_type ECMAScript = normal; static const regex_constants:: syntax_option_type JavaScript = normal; static const regex_constants:: syntax_option_type JScript = normal; static const regex_constants:: syntax_option_type basic = regex_constants::basic; static const regex_constants:: syntax_option_type extended = regex_constants::extended; static const regex_constants:: syntax_option_type awk = regex_constants::awk; static const regex_constants:: syntax_option_type grep = regex_constants::grep; static const regex_constants:: syntax_option_type egrep = regex_constants::egrep; static const regex_constants:: syntax_option_type sed = regex_constants::sed; static const regex_constants:: syntax_option_type perl = regex_constants::perl; static const regex_constants:: syntax_option_type literal = regex_constants::literal;

The meaning of these options is documented in the syntax_option_type section.

The static constant members are provided as synonyms for the constants declared in namespace boost::regex_constants; for each constant of type syntax_option_type declared in namespace boost::regex_constants then a constant with the same name, type and value is declared within the scope of basic_regex.

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basic_regex();

Effects: Constructs an object of class basic_regex.

Table 1. basic_regex default construction postconditions

Element Value

empty() true

size() 0

str() basic_string()

basic_regex(const charT* p, flag_type f = regex_constants::normal);

Requires: p shall not be a null pointer.

Throws: bad_expression if p is not a valid regular expression, unless the ¯ag no_except is set in f.

Effects: Constructs an object of class basic_regex; the object©s internal ®nite state machine is constructed from the regular expression contained in the null-terminated string p, and interpreted according to the option ¯ags speci®ed in f.

Table 2. Postconditions for basic_regex construction

Element Value

empty() false

size() char_traits::length(p)

str() basic_string(p)

flags() f

mark_count() The number of marked sub-expressions within the expression.

basic_regex(const charT* p1, const charT* p2, flag_type f = regex_constants::normal);

Requires: p1 and p2 are not null pointers, p1 < p2.

Throws: bad_expression if [p1,p2) is not a valid regular expression, unless the ¯ag no_except is set in f.

Effects: Constructs an object of class basic_regex; the object©s internal ®nite state machine is constructed from the regular expression contained in the sequence of characters [p1,p2), and interpreted according the option ¯ags speci®ed in f.

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Table 3. Postconditions for basic_regex construction

Element Value

empty() false

size() std::distance(p1,p2)

str() basic_string(p1,p2)

flags() f

mark_count() The number of marked sub-expressions within the expression.

basic_regex(const charT* p, size_type len, flag_type f);

Requires: p shall not be a null pointer, len < max_size().

Throws: bad_expression if p is not a valid regular expression, unless the ¯ag no_except is set in f.

Effects: Constructs an object of class basic_regex; the object©s internal ®nite state machine is constructed from the regular expression contained in the sequence of characters [p, p+len), and interpreted according the option ¯ags speci®ed in f.

Table 4. Postconditions for basic_regex construction

Element Value

empty() false

size() len

str() basic_string(p, len)

flags() f

mark_count() The number of marked sub-expressions within the expression.

basic_regex(const basic_regex& e);

Effects: Constructs an object of class basic_regex as a copy of the object e.

template basic_regex(const basic_string& s, flag_type f = regex_constants::normal);

Throws: bad_expression if s is not a valid regular expression, unless the ¯ag no_except is set in f.

Effects: Constructs an object of class basic_regex; the object©s internal ®nite state machine is constructed from the regular expression contained in the string s, and interpreted according to the option ¯ags speci®ed in f.

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Table 5. Postconditions for basic_regex construction

Element Value

empty() false

size() s.size()

str() s

flags() f

mark_count() The number of marked sub-expressions within the expression.

template basic_regex(ForwardIterator first, ForwardIterator last, flag_type f = regex_constants::normal);

Throws: bad_expression if the sequence [®rst, last) is not a valid regular expression, unless the ¯ag no_except is set in f.

Effects: Constructs an object of class basic_regex; the object©s internal ®nite state machine is constructed from the regular expression contained in the sequence of characters [®rst, last), and interpreted according to the option ¯ags speci®ed in f.

Table 6. Postconditions for basic_regex construction

Element Value

empty() false

size() distance(first,last)

str() basic_string(first,last)

flags() f

mark_count() The number of marked sub-expressions within the expression.

basic_regex& operator=(const basic_regex& e);

Effects: Returns the result of assign(e.str(), e.flags()).

basic_regex& operator=(const charT* ptr);

Requires: p shall not be a null pointer.

Effects: Returns the result of assign(ptr).

template basic_regex& operator=(const basic_string& p);

Effects: Returns the result of assign(p).

std::pair subexpression(size_type n) const;

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Effects: Returns a pair of iterators denoting the location of marked subexpression n within the original regular expression string. The returned iterators are relative to begin() and end().

Requires: The expression must have been compiled with the syntax_option_type save_subexpression_location set. Argument n must be in within the range 1 <= n < mark_count().

const_iterator begin() const;

Effects: Returns a starting iterator to a sequence of characters representing the regular expression.

const_iterator end() const;

Effects: Returns termination iterator to a sequence of characters representing the regular expression.

size_type size() const;

Effects: Returns the length of the sequence of characters representing the regular expression.

size_type max_size() const;

Effects: Returns the maximum length of the sequence of characters representing the regular expression.

bool empty() const;

Effects: Returns true if the object does not contain a valid regular expression, otherwise false.

size_type mark_count() const;

Effects: Returns the number of marked sub-expressions within the regular expresion.

basic_regex& assign(const basic_regex& that);

Effects: Returns assign(that.str(), that.flags()).

basic_regex& assign(const charT* ptr, flag_type f = regex_constants::normal);

Effects: Returns assign(string_type(ptr), f).

basic_regex& assign(const charT* ptr, unsigned int len, flag_type f);

Effects: Returns assign(string_type(ptr, len), f).

template basic_regex& assign(const basic_string& s, flag_type f = regex_constants::normal);

Throws: bad_expression if s is not a valid regular expression, unless the ¯ag no_except is set in f.

Returns: *this.

Effects: Assigns the regular expression contained in the string s, interpreted according the option ¯ags speci®ed in f.

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Table 7. Postconditions for basic_regex::assign

Element Value

empty() false

size() s.size()

str() s

flags() f

mark_count() The number of marked sub-expressions within the expression.

template basic_regex& assign(InputIterator first, InputIterator last, flag_type f = regex_constants::normal);

Requires: The type InputIterator corresponds to the Input Iterator requirements (24.1.1).

Effects: Returns assign(string_type(first, last), f).

flag_type flags() const;

Effects: Returns a copy of the regular expression syntax ¯ags that were passed to the object©s constructor, or the last call to assign.

int status() const;

Effects: Returns zero if the expression contains a valid regular expression, otherwise an error code. This member function is retained for use in environments that cannot use exception handling.

basic_string str() const;

Effects: Returns a copy of the character sequence passed to the object©s constructor, or the last call to assign.

int compare(basic_regex& e)const;

Effects: If flags() == e.flags() then returns str().compare(e.str()), otherwise returns flags() - e.flags().

locale_type imbue(locale_type l);

Effects: Returns the result of traits_inst.imbue(l) where traits_inst is a (default initialized) instance of the template parameter traits stored within the object. Calls to imbue invalidate any currently contained regular expression.

Postcondition: empty() == true.

locale_type getloc() const;

Effects: Returns the result of traits_inst.getloc() where traits_inst is a (default initialized) instance of the template parameter traits stored within the object.

void swap(basic_regex& e) throw();

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Effects: Swaps the contents of the two regular expressions.

Postcondition: *this contains the regular expression that was in e, e contains the regular expression that was in *this.

Complexity: constant time.

Note

Comparisons between basic_regex objects are provided on an experimental basis: please note that these are not present in the Technical Report on C++ Library Extensions, so use with care if you are writing code that may need to be ported to other implementations of basic_regex.

template bool operator == (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) == 0.

template bool operator != (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) != 0.

template bool operator < (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) < 0.

template bool operator <= (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) <= 0.

template bool operator >= (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) >= 0.

template bool operator > (const basic_regex& lhs, const basic_regex& rhs);

Effects: Returns lhs.compare(rhs) > 0.

Note

The basic_regex stream inserter is provided on an experimental basis, and outputs the textual representation of the expression to the stream.

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template basic_ostream& operator << (basic_ostream& os const basic_regex& e);

Effects: Returns (os << e.str()).

template void swap(basic_regex& lhs, basic_regex& rhs);

Effects: calls lhs.swap(rhs). match_results

Synopsis

#include

Regular expressions are different from many simple pattern-matching algorithms in that as well as ®nding an overall match they can also produce sub-expression matches: each sub-expression being delimited in the pattern by a pair of parenthesis (...). There has to be some method for reporting sub-expression matches back to the user: this is achieved this by de®ning a class match_results that acts as an indexed collection of sub-expression matches, each sub-expression match being contained in an object of type sub_match.

Template class match_results denotes a collection of character sequences representing the result of a regular expression match. Objects of type match_results are passed to the algorithms regex_match and regex_search, and are returned by the iterator regex_iterator. Storage for the collection is allocated and freed as necessary by the member functions of class match_results.

The template class match_results conforms to the requirements of a Sequence, as speci®ed in (lib.sequence.reqmts), except that only operations de®ned for const-quali®ed Sequences are supported.

Class template match_results is most commonly used as one of the typedefs cmatch, wcmatch, smatch, or wsmatch:

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template > class match_results; typedef match_results cmatch; typedef match_results wcmatch; typedef match_results smatch; typedef match_results wsmatch; template > class match_results { public: typedef sub_match value_type; typedef const value_type& const_reference; typedef const_reference reference; typedef implementation defined const_iterator; typedef const_iterator iterator; typedef typename iterator_traits::difference_type difference_type; typedef typename Allocator::size_type size_type; typedef Allocator allocator_type; typedef typename iterator_traits::value_type char_type; typedef basic_string string_type;

// construct/copy/destroy: explicit match_results(const Allocator& a = Allocator()); match_results(const match_results& m); match_results& operator=(const match_results& m); ~match_results();

// size: size_type size() const; size_type max_size() const; bool empty() const; // element access: difference_type length(int sub = 0) const; difference_type length(const char_type* sub) const; template difference_type length(const charT* sub) const; template difference_type length(const std::basic_string& sub) const; difference_type position(unsigned int sub = 0) const; difference_type position(const char_type* sub) const; template difference_type position(const charT* sub) const; template difference_type position(const std::basic_string& sub) const; string_type str(int sub = 0) const; string_type str(const char_type* sub)const; template string_type str(const std::basic_string& sub)const; template string_type str(const charT* sub)const; template string_type str(const std::basic_string& sub)const; const_reference operator[](int n) const; const_reference operator[](const char_type* n) const; template const_reference operator[](const std::basic_string& n) const; template const_reference operator[](const charT* n) const; template

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const_reference operator[](const std::basic_string& n) const;

const_reference prefix() const;

const_reference suffix() const; const_iterator begin() const; const_iterator end() const; // format: template OutputIterator format(OutputIterator out, Formatter fmt, match_flag_type flags = format_default) const; template string_type format(Formatter fmt, match_flag_type flags = format_default) const;

allocator_type get_allocator() const; void swap(match_results& that);

#ifdef BOOST_REGEX_MATCH_EXTRA typedef typename value_type::capture_sequence_type capture_sequence_type; const capture_sequence_type& captures(std::size_t i)const; #endif

};

template bool operator == (const match_results& m1, const match_results& m2); template bool operator != (const match_results& m1, const match_results& m2);

template basic_ostream& operator << (basic_ostream& os, const match_results& m);

template void swap(match_results& m1, match_results& m2);

Description

In all match_results constructors, a copy of the Allocator argument is used for any memory allocation performed by the constructor or member functions during the lifetime of the object.

match_results(const Allocator& a = Allocator());

Effects: Constructs an object of class match_results. The postconditions of this function are indicated in the table:

Element Value

empty() true

size() 0

str() basic_string()

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match_results(const match_results& m);

Effects: Constructs an object of class match_results, as a copy of m.

match_results& operator=(const match_results& m);

Effects: Assigns m to *this. The postconditions of this function are indicated in the table:

Element Value

empty() m.empty().

size() m.size().

str(n) m.str(n) for all integers n < m.size().

pre®x() m.pre®x().

suf®x() m.suf®x().

(*this)[n] m[n] for all integers n < m.size().

length(n) m.length(n) for all integers n < m.size().

position(n) m.position(n) for all integers n < m.size().

size_type size()const;

Effects: Returns the number of sub_match elements stored in *this; that is the number of marked sub-expressions in the regular expression that was matched plus one.

size_type max_size()const;

Effects: Returns the maximum number of sub_match elements that can be stored in *this.

bool empty()const;

Effects: Returns size() == 0.

difference_type length(int sub = 0)const; difference_type length(const char_type* sub)const; template difference_type length(const charT* sub)const; template difference_type length(const std::basic_string&)const;

Requires: that the match_results object has been initialized as a result of a successful call to regex_search or regex_match or was returned from a regex_iterator, and that the underlying iterators have not been subsequently invalidated. Will raise a std::logic_error if the match_results object was not initialized.

Effects: Returns the length of sub-expression sub, that is to say: (*this)[sub].length().

The overloads that accept a string refer to a named sub-expression n. In the event that there is no such named sub-expression then returns zero.

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The template overloads of this function, allow the string and/or character type to be different from the character type of the underlying sequence and/or regular expression: in this case the characters will be widened to the underlying character type of the original regular expression. A compiler error will occur if the argument passes a wider character type than the underlying sequence. These overloads allow a normal narrow character C string literal to be used as an argument, even when the underlying character type of the expression being matched may be something more exotic such as a Unicode character type.

difference_type position(unsigned int sub = 0)const; difference_type position(const char_type* sub)const; template difference_type position(const charT* sub)const; template difference_type position(const std::basic_string&)const;

Effects: Returns the starting location of sub-expression sub, or -1 if sub was not matched. Note that if this represents a partial match , then position() will return the location of the partial match even though (*this)[0].matched is false.

The overloads that accept a string refer to a named sub-expression n. In the event that there is no such named sub-expression then returns -1.

string_type str(int sub = 0)const; string_type str(const char_type* sub)const; template string_type str(const std::basic_string& sub)const; template string_type str(const charT* sub)const; template string_type str(const std::basic_string& sub)const;

Effects: Returns sub-expression sub as a string: string_type((*this)[sub]).

The overloads that accept a string, return the string that matched the named sub-expression n. In the event that there is no such named sub-expression then returns an empty string.

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const_reference operator[](int n) const; const_reference operator[](const char_type* n) const; template const_reference operator[](const std::basic_string& n) const; template const_reference operator[](const charT* n) const; template const_reference operator[](const std::basic_string& n) const;

Effects: Returns a reference to the sub_match object representing the character sequence that matched marked sub-expression n. If n == 0 then returns a reference to a sub_match object representing the character sequence that matched the whole regular expression. If n is out of range, or if n is an unmatched sub-expression, then returns a sub_match object whose matched member is false.

The overloads that accept a string, return a reference to the sub_match object representing the character sequence that matched the named sub-expression n. In the event that there is no such named sub-expression then returns a sub_match object whose matched member is false.

const_reference prefix()const;

Effects: Returns a reference to the sub_match object representing the character sequence from the start of the string being matched or searched, to the start of the match found.

const_reference suffix()const;

Effects: Returns a reference to the sub_match object representing the character sequence from the end of the match found to the end of the string being matched or searched.

const_iterator begin()const;

Effects: Returns a starting iterator that enumerates over all the marked sub-expression matches stored in *this.

const_iterator end()const;

Effects: Returns a terminating iterator that enumerates over all the marked sub-expression matches stored in *this.

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template OutputIterator format(OutputIterator out, Formatter fmt, match_flag_type flags = format_default);

Requires: The type OutputIterator conforms to the Output Iterator requirements (C++ std 24.1.2).

The type Formatter must be either a pointer to a null-terminated string of type char_type[], or be a container of char_type©s (for example std::basic_string) or be a unary, binary or ternary functor that computes the replacement string from a function call: either fmt(*this) which must return a container of char_type©s to be used as the replacement text, or either fmt(*this, out) or fmt(*this, out, flags), both of which write the replacement text to *out, and then return the new OutputIterator position. Note that if the formatter is a functor, then it is passed by value: users that want to pass function objects with internal state might want to use Boost.Ref to wrap the object so that it©s passed by reference.

Effects: If fmt is either a null-terminated string, or a container of char_type©s, then copies the character sequence [fmt.begin(), fmt.end()) to OutputIterator out. For each format speci®er or escape sequence in fmt, replace that sequence with either the character(s) it represents, or the sequence of characters within *this to which it refers. The bitmasks speci®ed in ¯ags determines what format speci®ers or escape sequences are recognized, by default this is the format used by ECMA-262, ECMAScript Language Speci®cation, Chapter 15 part 5.4.11 String.prototype.replace.

If fmt is a function object, then depending on the number of arguments the function object accepts, it will either:

· Call fmt(*this) and copy the string returned to OutputIterator out.

· Call fmt(*this, out).

· Call fmt(*this, out, flags).

In all cases the new position of the OutputIterator is returned.

See the format syntax guide for more information.

Returns: out.

template string_type format(Formatter fmt, match_flag_type flags = format_default);

Effects: If fmt is either a null-terminated string, or a container of char_type©s, then copies the string fmt: For each format speci®er or escape sequence in fmt, replace that sequence with either the character(s) it represents, or the sequence of characters within *this to which it refers. The bitmasks speci®ed in ¯ags determines what format speci®ers or escape sequences are recognized, by default this is the format used by ECMA-262, ECMAScript Language Speci®cation, Chapter 15 part 5.4.11 String.prototype.replace.

If fmt is a function object, then depending on the number of arguments the function object accepts, it will either:

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· Call fmt(*this) and return the result.

· Call fmt(*this, unspecified-output-iterator), where unspecified-output-iterator is an unspeci®ed OutputIter- ator type used to copy the output to the string result.

· Call fmt(*this, unspecified-output-iterator, flags), where unspecified-output-iterator is an unspeci®ed OutputIterator type used to copy the output to the string result.

See the format syntax guide for more information.

allocator_type get_allocator()const;

Effects: Returns a copy of the Allocator that was passed to the object©s constructor.

void swap(match_results& that);

Effects: Swaps the contents of the two sequences.

Postcondition: *this contains the sequence of matched sub-expressions that were in that, that contains the sequence of matched sub- expressions that were in *this.

Complexity: constant time.

typedef typename value_type::capture_sequence_type capture_sequence_type;

De®nes an implementation-speci®c type that satis®es the requirements of a standard library Sequence (21.1.1 including the optional Table 68 operations), whose value_type is a sub_match. This type happens to be std::vector >, but you shouldn©t actually rely on that.

const capture_sequence_type& captures(std::size_t i)const;

Effects: returns a sequence containing all the captures obtained for sub-expression i.

Returns: (*this)[i].captures();

Preconditions: the library must be built and used with BOOST_REGEX_MATCH_EXTRA de®ned, and you must pass the ¯ag match_extra to the regex matching functions ( regex_match, regex_search, regex_iterator or regex_token_iterator) in order for this member function to be de®ned and return useful information.

Rationale: Enabling this feature has several consequences:

· sub_match occupies more memory resulting in complex expressions running out of memory or stack space more quickly during matching.

· The matching algorithms are less ef®cient at handling some features (independent sub-expressions for example), even when match_extra is not used.

· The matching algorithms are much less ef®cient (i.e. slower), when match_extra is used. Mostly this is down to the extra memory allocations that have to take place.

template bool operator == (const match_results& m1, const match_results& m2);

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Effects: Compares the two sequences for equality.

template bool operator != (const match_results& m1, const match_results& m2);

Effects: Compares the two sequences for inequality.

template basic_ostream& operator << (basic_ostream& os, const match_results& m);

Effects: Writes the contents of m to the stream os as if by calling os << m.str(); Returns os.

template void swap(match_results& m1, match_results& m2);

Effects: Swaps the contents of the two sequences. sub_match

#include

Objects of type sub_match may only be obtained by subscripting an object of type match_results.

Objects of type sub_match may be compared to objects of type std::basic_string, or const charT* or const charT.

Objects of type sub_match may be added to objects of type std::basic_string, or const charT* or const charT, to produce a new std::basic_string object.

When the marked sub-expression denoted by an object of type sub_match participated in a regular expression match then member matched evaluates to true, and members ®rst and second denote the range of characters [®rst,second) which formed that match. Otherwise matched is false, and members ®rst and second contained unde®ned values.

When the marked sub-expression denoted by an object of type sub_match was repeated, then the sub_match object represents the match obtained by the last repeat. The complete set of all the captures obtained for all the repeats, may be accessed via the captures() member function (Note: this has serious performance implications, you have to explicitly enable this feature).

If an object of type sub_match represents sub-expression 0 - that is to say the whole match - then member matched is always true, unless a partial match was obtained as a result of the ¯ag match_partial being passed to a regular expression algorithm, in which case member matched is false, and members ®rst and second represent the character range that formed the partial match.

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namespace boost{ template class sub_match; typedef sub_match csub_match; typedef sub_match wcsub_match; typedef sub_match ssub_match; typedef sub_match wssub_match; template class sub_match : public std::pair { public: typedef typename iterator_traits::value_type value_type; typedef typename iterator_traits::difference_type difference_type; typedef BidirectionalIterator iterator;

bool matched;

difference_type length()const; operator basic_string()const; basic_string str()const;

int compare(const sub_match& s)const; int compare(const basic_string& s)const; int compare(const value_type* s)const; #ifdef BOOST_REGEX_MATCH_EXTRA typedef implementation-private capture_sequence_type; const capture_sequence_type& captures()const; #endif }; // // comparisons to another sub_match: // template bool operator == (const sub_match& lhs, const sub_match& rhs); template bool operator != (const sub_match& lhs, const sub_match& rhs); template bool operator < (const sub_match& lhs, const sub_match& rhs); template bool operator <= (const sub_match& lhs, const sub_match& rhs); template bool operator >= (const sub_match& lhs, const sub_match& rhs); template bool operator > (const sub_match& lhs, const sub_match& rhs);

// // comparisons to a basic_string: // template bool operator == (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

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template bool operator != (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs); template bool operator < (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs); template bool operator > (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs); template bool operator >= (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs); template bool operator <= (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs); template bool operator == (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs); template bool operator != (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs); template bool operator < (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs); template bool operator > (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs); template bool operator >= (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs); template bool operator <= (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

// // comparisons to a pointer to a character array: // template bool operator == (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

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template bool operator != (typename iterator_traits::value_type const* lhs, const sub_match& rhs); template bool operator < (typename iterator_traits::value_type const* lhs, const sub_match& rhs); template bool operator > (typename iterator_traits::value_type const* lhs, const sub_match& rhs); template bool operator >= (typename iterator_traits::value_type const* lhs, const sub_match& rhs); template bool operator <= (typename iterator_traits::value_type const* lhs, const sub_match& rhs); template bool operator == (const sub_match& lhs, typename iterator_traits::value_type const* rhs); template bool operator != (const sub_match& lhs, typename iterator_traits::value_type const* rhs); template bool operator < (const sub_match& lhs, typename iterator_traits::value_type const* rhs); template bool operator > (const sub_match& lhs, typename iterator_traits::value_type const* rhs); template bool operator >= (const sub_match& lhs, typename iterator_traits::value_type const* rhs); template bool operator <= (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

// // comparisons to a single character: // template bool operator == (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator != (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator < (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator > (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator >= (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator <= (typename iterator_traits::value_type const& lhs, const sub_match& rhs); template bool operator == (const sub_match& lhs, typename iterator_traits::value_type const& rhs); template bool operator != (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

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template bool operator < (const sub_match& lhs, typename iterator_traits::value_type const& rhs); template bool operator > (const sub_match& lhs, typename iterator_traits::value_type const& rhs); template bool operator >= (const sub_match& lhs, typename iterator_traits::value_type const& rhs); template bool operator <= (const sub_match& lhs, typename iterator_traits::value_type const& rhs); // // addition operators: // template std::basic_string::value_type, traits, Allocator> operator + (const std::basic_string::value_type, traits, Allocator>& s, const sub_match& m); template std::basic_string::value_type, traits, Allocator> operator + (const sub_match& m, const std::basic_string::value_type, traits, Allocator>& s); template std::basic_string::value_type> operator + (typename iterator_traits::value_type const* s, const sub_match& m); template std::basic_string::value_type> operator + (const sub_match& m, typename iterator_traits::value_type const * s); template std::basic_string::value_type> operator + (typename iterator_traits::value_type const& s, const sub_match& m); template std::basic_string::value_type> operator + (const sub_match& m, typename iterator_traits::value_type const& s); template std::basic_string::value_type> operator + (const sub_match& m1, const sub_match& m2);

// // stream inserter: // template basic_ostream& operator << (basic_ostream& os, const sub_match& m);

} // namespace boost

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Description

Members

typedef typename std::iterator_traits::value_type value_type;

The type pointed to by the iterators.

typedef typename std::iterator_traits::difference_type difference_type;

A type that represents the difference between two iterators.

typedef BidirectionalIterator iterator;

The iterator type.

iterator first

An iterator denoting the position of the start of the match.

iterator second

An iterator denoting the position of the end of the match.

bool matched

A Boolean value denoting whether this sub-expression participated in the match.

static difference_type length();

Effects: returns the length of this matched sub-expression, or 0 if this sub-expression was not matched: matched ? distance(first, second) : 0).

operator basic_string()const;

Effects: converts *this into a string: returns (matched ? basic_string(first, second) : ba- sic_string()).

basic_string str()const;

Effects: returns a string representation of *this: (matched ? basic_string(first, second) : ba- sic_string()).

int compare(const sub_match& s)const;

Effects: performs a lexical comparison to s: returns str().compare(s.str()).

int compare(const basic_string& s)const;

Effects: compares *this to the string s: returns str().compare(s).

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int compare(const value_type* s)const;

Effects: compares *this to the null-terminated string s: returns str().compare(s).

typedef implementation-private capture_sequence_type;

const capture_sequence_type& captures()const;

Effects: returns a sequence containing all the captures obtained for this sub-expression.

Preconditions: the library must be built and used with BOOST_REGEX_MATCH_EXTRA de®ned, and you must pass the ¯ag match_extra to the regex matching functions ( regex_match, regex_search, regex_iterator or regex_token_iterator) in order for this member #function to be de®ned and return useful information.

Rationale: Enabling this feature has several consequences:

· sub_match occupies more memory resulting in complex expressions running out of memory or stack space more quickly during matching.

· The matching algorithms are less ef®cient at handling some features (independent sub-expressions for example), even when match_extra is not used.

· The matching algorithms are much less ef®cient (i.e. slower), when match_extra is used. Mostly this is down to the extra memory allocations that have to take place. sub_match non-member operators

template bool operator == (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) == 0.

template bool operator != (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) != 0.

template bool operator < (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) < 0.

template bool operator <= (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) <= 0.

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template bool operator >= (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) >= 0.

template bool operator > (const sub_match& lhs, const sub_match& rhs);

Effects: returns lhs.compare(rhs) > 0.

template bool operator == (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs == rhs.str().

template bool operator != (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs != rhs.str().

template bool operator < (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs < rhs.str().

template bool operator > (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs > rhs.str().

template bool operator >= (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs >= rhs.str().

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template bool operator <= (const std::basic_string::value_type, traits, Allocator>& lhs, const sub_match& rhs);

Effects: returns lhs <= rhs.str().

template bool operator == (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() == rhs.

template bool operator != (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() != rhs.

template bool operator < (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() < rhs.

template bool operator > (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() > rhs.

template bool operator >= (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() >= rhs.

template bool operator <= (const sub_match& lhs, const std::basic_string::value_type, traits, Allocator>& rhs);

Effects: returns lhs.str() <= rhs.

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template bool operator == (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs == rhs.str().

template bool operator != (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs != rhs.str().

template bool operator < (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs < rhs.str().

template bool operator > (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs > rhs.str().

template bool operator >= (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs >= rhs.str().

template bool operator <= (typename iterator_traits::value_type const* lhs, const sub_match& rhs);

Effects: returns lhs <= rhs.str().

template bool operator == (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() == rhs.

template bool operator != (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() != rhs.

template bool operator < (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() < rhs.

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template bool operator > (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() > rhs.

template bool operator >= (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() >= rhs.

template bool operator <= (const sub_match& lhs, typename iterator_traits::value_type const* rhs);

Effects: returns lhs.str() <= rhs.

template bool operator == (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs == rhs.str().

template bool operator != (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs != rhs.str().

template bool operator < (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs < rhs.str().

template bool operator > (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs > rhs.str().

template bool operator >= (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs >= rhs.str().

template bool operator <= (typename iterator_traits::value_type const& lhs, const sub_match& rhs);

Effects: returns lhs <= rhs.str().

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template bool operator == (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() == rhs.

template bool operator != (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() != rhs.

template bool operator < (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() < rhs.

template bool operator > (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() > rhs.

template bool operator >= (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() >= rhs.

template bool operator <= (const sub_match& lhs, typename iterator_traits::value_type const& rhs);

Effects: returns lhs.str() <= rhs.

The addition operators for sub_match allow you to add a sub_match to any type to which you can add a std::string and obtain a new string as the result.

template std::basic_string::value_type, traits, Allocator> operator + (const std::basic_string::value_type, traits, Allocator>& s, const sub_match& m);

Effects: returns s + m.str().

template std::basic_string::value_type, traits, Allocator> operator + (const sub_match& m, const std::basic_string::value_type, traits, Allocator>& s);

Effects: returns m.str() + s.

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template std::basic_string::value_type> operator + (typename iterator_traits::value_type const* s, const sub_match& m);

Effects: returns s + m.str().

template std::basic_string::value_type> operator + (const sub_match& m, typename iterator_traits::value_type const * s);

Effects: returns m.str() + s.

template std::basic_string::value_type> operator + (typename iterator_traits::value_type const& s, const sub_match& m);

Effects: returns s + m.str().

template std::basic_string::value_type> operator + (const sub_match& m, typename iterator_traits::value_type const& s);

Effects: returns m.str() + s.

template std::basic_string::value_type> operator + (const sub_match& m1, const sub_match& m2);

Effects: returns m1.str() + m2.str().

Stream inserter

template basic_ostream& operator << (basic_ostream& os const sub_match& m);

Effects: returns (os << m.str()). regex_match

#include

The algorithm regex_match determines whether a given regular expression matches all of a given character sequence denoted by a pair of bidirectional-iterators, the algorithm is de®ned as follows, the main use of this function is data input validation.

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Important

Note that the result is true only if the expression matches the whole of the input sequence. If you want to search for an expression somewhere within the sequence then use regex_search. If you want to match a pre®x of the character string then use regex_search with the ¯ag match_continuous set.

template bool regex_match(BidirectionalIterator first, BidirectionalIterator last, match_results& m, const basic_regex & e, match_flag_type flags = match_default);

template bool regex_match(BidirectionalIterator first, BidirectionalIterator last, const basic_regex & e, match_flag_type flags = match_default);

template bool regex_match(const charT* str, match_results& m, const basic_regex & e, match_flag_type flags = match_default);

template bool regex_match(const basic_string& s, match_results::const_iterator, Allocator>& m, const basic_regex & e, match_flag_type flags = match_default);

template bool regex_match(const charT* str, const basic_regex & e, match_flag_type flags = match_default);

template bool regex_match(const basic_string& s, const basic_regex & e, match_flag_type flags = match_default);

Description

template bool regex_match(BidirectionalIterator first, BidirectionalIterator last, match_results& m, const basic_regex & e, match_flag_type flags = match_default);

Requires: Type BidirectionalIterator meets the requirements of a Bidirectional Iterator (24.1.4).

Effects: Determines whether there is an exact match between the regular expression e, and all of the character sequence [®rst, last), parameter ¯ags (see match_flag_type) is used to control how the expression is matched against the character sequence. Returns true if such a match exists, false otherwise.

Throws: std::runtime_error if the complexity of matching the expression against an N character string begins to exceed O(N2), or if the program runs out of stack space while matching the expression (if Boost.Regex is con®gured in recursive mode), or if the matcher exhausts its permitted memory allocation (if Boost.Regex is con®gured in non-recursive mode).

Postconditions: If the function returns false, then the effect on parameter m is unde®ned, otherwise the effects on parameter m are given in the table:

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Element Value

m.size() e.mark_count()

m.empty() false

m.prefix().first first

m.prefix().last first

m.prefix().matched false

m.suffix().first last

m.suffix().last last

m.suffix().matched false

m[0].first first

m[0].second last

m[0].matched true if a full match was found, and false if it was a partial match (found as a result of the match_partial ¯ag being set).

m[n].first For all integers n < m.size(), the start of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

m[n].second For all integers n < m.size(), the end of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

m[n].matched For all integers n < m.size(), true if sub-expression n participated in the match, false otherwise.

template bool regex_match(BidirectionalIterator first, BidirectionalIterator last, const basic_regex & e, match_flag_type flags = match_default);

Effects: Behaves "as if" by constructing an instance of match_results what, and then returning the result of regex_match(first, last, what, e, flags).

template bool regex_match(const charT* str, match_results& m, const basic_regex & e, match_flag_type flags = match_default);

Effects: Returns the result of regex_match(str, str + char_traits::length(str), m, e, flags).

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template bool regex_match(const basic_string& s, match_results::const_iterator, Allocator>& m, const basic_regex & e, match_flag_type flags = match_default);

Effects: Returns the result of regex_match(s.begin(), s.end(), m, e, flags).

template bool regex_match(const charT* str, const basic_regex & e, match_flag_type flags = match_default);

Effects: Returns the result of regex_match(str, str + char_traits::length(str), e, flags).

template bool regex_match(const basic_string& s, const basic_regex & e, match_flag_type flags = match_default);

Effects: Returns the result of regex_match(s.begin(), s.end(), e, flags).

Examples

The following example processes an ftp response:

#include #include #include #include

using namespace boost;

regex expression("([0-9]+)(\\-| |$)(.*)");

// process_ftp: // on success returns the ftp response code, and fills // msg with the ftp response message. int process_ftp(const char* response, std::string* msg) { cmatch what; if(regex_match(response, what, expression)) { // what[0] contains the whole string // what[1] contains the response code // what[2] contains the separator character // what[3] contains the text message. if(msg) msg->assign(what[3].first, what[3].second); return std::atoi(what[1].first); } // failure did not match if(msg) msg->erase(); return -1; }

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#include

The algorithm regex_search will search a range denoted by a pair of bidirectional-iterators for a given regular expression. The algorithm uses various heuristics to reduce the search time by only checking for a match if a match could conceivably start at that position. The algorithm is de®ned as follows:

template bool regex_search(BidirectionalIterator first, BidirectionalIterator last, match_results& m, const basic_regex& e, match_flag_type flags = match_default);

template bool regex_search(const basic_string& s, match_results< typename basic_string::const_iterator, Allocator>& m, const basic_regex& e, match_flag_type flags = match_default);

template bool regex_search(const charT* str, match_results& m, const basic_regex& e, match_flag_type flags = match_default);

template bool regex_search(BidirectionalIterator first, BidirectionalIterator last, const basic_regex& e, match_flag_type flags = match_default);

template bool regex_search(const charT* str, const basic_regex& e, match_flag_type flags = match_default);

template bool regex_search(const basic_string& s, const basic_regex& e, match_flag_type flags = match_default);

Description

template bool regex_search(BidirectionalIterator first, BidirectionalIterator last, match_results& m, const basic_regex& e, match_flag_type flags = match_default);

Requires: Type BidirectionalIterator meets the requirements of a Bidirectional Iterator (24.1.4).

Effects: Determines whether there is some sub-sequence within [®rst,last) that matches the regular expression e, parameter ¯ags is used to control how the expression is matched against the character sequence. Returns true if such a sequence exists, false otherwise.

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Postconditions: If the function returns false, then the effect on parameter m is unde®ned, otherwise the effects on parameter m are given in the table:

Element Value

m.size() e.mark_count()

m.empty() false

m.prefix().first first

m.prefix().last m[0].first

m.prefix().matched m.prefix().first != m.prefix().second

m.suffix().first m[0].second

m.suffix().last last

m.suffix().matched m.suffix().first != m.suffix().second

m[0].first The start of the sequence of characters that matched the regular expression

m[0].second The end of the sequence of characters that matched the regular expression

m[0].matched true if a full match was found, and false if it was a partial match (found as a result of the match_partial ¯ag being set).

m[n].first For all integers n < m.size(), the start of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

m[n].second For all integers n < m.size(), the end of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

m[n].matched For all integers n < m.size(), true if sub-expression n participated in the match, false otherwise.

template bool regex_search(const charT* str, match_results& m, const basic_regex& e, match_flag_type flags = match_default);

Effects: Returns the result of regex_search(str, str + char_traits::length(str), m, e, flags).

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template bool regex_search(const basic_string& s, match_results::const_iterator, Allocat↵ or>& m, const basic_regex& e, match_flag_type flags = match_default);

Effects: Returns the result of regex_search(s.begin(), s.end(), m, e, flags).

template bool regex_search(iterator first, iterator last, const basic_regex& e, match_flag_type flags = match_default);

Effects: Behaves "as if" by constructing an instance of match_results what, and then returning the result of regex_search(first, last, what, e, flags).

template bool regex_search(const charT* str const basic_regex& e, match_flag_type flags = match_default);

Effects: Returns the result of regex_search(str, str + char_traits::length(str), e, flags).

template bool regex_search(const basic_string& s, const basic_regex& e, match_flag_type flags = match_default);

Effects: Returns the result of regex_search(s.begin(), s.end(), e, flags).

Examples

The following example, takes the contents of a ®le in the form of a string, and searches for all the C++ class declarations in the ®le. The code will work regardless of the way that std::string is implemented, for example it could easily be modi®ed to work with the SGI rope class, which uses a non-contiguous storage strategy.

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#include #include #include

boost::regex expression( "^(template[[:space:]]*<[^;:{]+>[[:space:]]*)?" "(class|struct)[[:space:]]*" "(\\<\\w+\\>([[:blank:]]*\$[^)]*\$)?" "[[:space:]]*)*(\\<\\w*\\>)[[:space:]]*" "(<[^;:{]+>[[:space:]]*)?(\\{|:[^;\\{()]*\\{)");

void IndexClasses(map_type& m, const std::string& file) { std::string::const_iterator start, end; start = file.begin(); end = file.end(); boost::match_results what; boost::match_flag_type flags = boost::match_default; while(regex_search(start, end, what, expression, flags)) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: m[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] = what[5].first - file.begin(); // update search position: start = what[0].second; // update flags: flags |= boost::match_prev_avail; flags |= boost::match_not_bob; } } regex_replace

#include

The algorithm regex_replace searches through a string ®nding all the matches to the regular expression: for each match it then calls match_results<>::format to format the string and sends the result to the output iterator. Sections of text that do not match are copied to the output unchanged only if the ¯ags parameter does not have the ¯ag format_no_copy set. If the ¯ag format_first_only is set then only the ®rst occurrence is replaced rather than all occurrences.

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template OutputIterator regex_replace(OutputIterator out, BidirectionalIterator first, BidirectionalIterator last, const basic_regex& e, Formatter fmt, match_flag_type flags = match_default);

template basic_string regex_replace(const basic_string& s, const basic_regex& e, Formatter fmt, match_flag_type flags = match_default);

Description

template OutputIterator regex_replace(OutputIterator out, BidirectionalIterator first, BidirectionalIterator last, const basic_regex& e, Formatter fmt, match_flag_type flags = match_default);

Enumerates all the occurences of expression e in the sequence [®rst, last), replacing each occurence with the string that results by merging the match found with the format string fmt, and copies the resulting string to out. In the case that fmt is a unary, binary or ternary function object, then the character sequence generated by that object is copied unchanged to the output when performing a substitution.

If the ¯ag format_no_copy is set in ¯ags then unmatched sections of text are not copied to output.

If the ¯ag format_first_only is set in ¯ags then only the ®rst occurence of e is replaced.

The manner in which the format string fmt is interpretted, along with the rules used for ®nding matches, are determined by the ¯ags set in ¯ags: see match_flag_type.

Requires The type Formatter must be either a pointer to a null-terminated string of type char_type[], or be a container of char_type©s (for example std::basic_string) or be a unary, binary or ternary functor that computes the replacement string from a function call: either fmt(what) which must return a container of char_type©s to be used as the replacement text, or either fmt(what, out) or fmt(what, out, flags), both of which write the replacement text to *out, and then return the new OutputIterator position. In each case what is the match_results object that represents the match found. Note that if the formatter is a functor, then it is passed by value: users that want to pass function objects with internal state might want to use Boost.Ref to wrap the object so that it©s passed by reference.

Effects: Constructs an regex_iterator object:

regex_iterator i(first, last, e, flags), and uses i to enumerate through all of the matches m of type match_results that occur within the sequence [®rst, last).

If no such matches are found and

!(flags & format_no_copy) then calls

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std::copy(first, last, out).

Otherwise, for each match found, if

!(flags & format_no_copy) calls

std::copy(m.prefix().first, m.prefix().last, out), and then calls

m.format(out, fmt, flags).

Finally if

!(flags & format_no_copy) calls

std::copy(last_m.suffix().first, last_m,suffix().last, out) where last_m is a copy of the last match found.

If flags & format_first_only is non-zero then only the ®rst match found is replaced.

Returns: out.

template basic_string regex_replace(const basic_string& s, const basic_regex& e, Formatter fmt, match_flag_type flags = match_default);

Effects: Constructs an object basic_string result, calls regex_replace(back_inserter(result), s.begin(), s.end(), e, fmt, flags), and then returns result.

Examples

The following example takes C/C++ source code as input, and outputs syntax highlighted HTML code.

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#include #include #include #include #include #include #include

// purpose: // takes the contents of a file and transform to // syntax highlighted code in html format boost::regex e1, e2; extern const char* expression_text; extern const char* format_string; extern const char* pre_expression; extern const char* pre_format; extern const char* header_text; extern const char* footer_text; void load_file(std::string& s, std::istream& is) { s.erase(); s.reserve(is.rdbuf()->in_avail()); char c; while(is.get(c)) { if(s.capacity() == s.size()) s.reserve(s.capacity() * 3); s.append(1, c); } } int main(int argc, const char** argv) { try{ e1.assign(expression_text); e2.assign(pre_expression); for(int i = 1; i < argc; ++i) { std::cout << "Processing file " << argv[i] << std::endl; std::ifstream fs(argv[i]); std::string in; load_file(in, fs); std::string out_name(std::string(argv[i]) + std::string(".htm")); std::ofstream os(out_name.c_str()); os << header_text; // strip ©<© and ©>© first by outputting to a // temporary string stream std::ostringstream t(std::ios::out | std::ios::binary); std::ostream_iterator oi(t); boost::regex_replace(oi, in.begin(), in.end(), e2, pre_format, boost::match_default | boost::format_all); // then output to final output stream // adding syntax highlighting: std::string s(t.str()); std::ostream_iterator out(os); boost::regex_replace(out, s.begin(), s.end(), e1, format_string, boost::match_default | boost::format_all); os << footer_text; } } catch(...)

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{ return -1; } return 0; }

extern const char* pre_expression = "(<)|(>)|(&)|\\r"; extern const char* pre_format = "(?1<)(?2>)(?3&)";

const char* format_string = "(?1$&)" "(?2$&)" "(?3$&)" "(?4$&)" "(?5$&)";

const char* header_text = "\n\n" "Auto-generated html formated source\n" "\n" "\n" "\n" "

";
 const char* footer_text = "

\n\n\n"; regex_iterator

The iterator type regex_iterator will enumerate all of the regular expression matches found in some sequence: dereferencing a regex_iterator yields a reference to a match_results object.

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template ::value_type, class traits = regex_traits > class regex_iterator { public: typedef basic_regex regex_type; typedef match_results value_type; typedef typename iterator_traits::difference_type difference_type; typedef const value_type* pointer; typedef const value_type& reference; typedef std::forward_iterator_tag iterator_category;

regex_iterator(); regex_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, match_flag_type m = match_default); regex_iterator(const regex_iterator&); regex_iterator& operator=(const regex_iterator&); bool operator==(const regex_iterator&)const; bool operator!=(const regex_iterator&)const; const value_type& operator*()const; const value_type* operator->()const; regex_iterator& operator++(); regex_iterator operator++(int); };

typedef regex_iterator cregex_iterator; typedef regex_iterator sregex_iterator;

#ifndef BOOST_NO_WREGEX typedef regex_iterator wcregex_iterator; typedef regex_iterator wsregex_iterator; #endif

template regex_iterator make_regex_iterator(const charT* p, const basic_regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

template regex_iterator::const_iterator, charT, traits> make_regex_iterator(const std::basic_string& p, const basic_regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

Description

A regex_iterator is constructed from a pair of iterators, and enumerates all occurrences of a regular expression within that iterator range.

regex_iterator();

Effects: constructs an end of sequence regex_iterator.

regex_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, match_flag_type m = match_default);

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Effects: constructs a regex_iterator that will enumerate all occurrences of the expression re, within the sequence [a,b), and found using match_flag_type m. The object re must exist for the lifetime of the regex_iterator.

regex_iterator(const regex_iterator& that);

Effects: constructs a copy of that.

Postconditions: *this == that.

regex_iterator& operator=(const regex_iterator&);

Effects: sets *this equal to those in that.

Postconditions: *this == that.

bool operator==(const regex_iterator& that)const;

Effects: returns true if *this is equal to that.

bool operator!=(const regex_iterator&)const;

Effects: returns !(*this == that).

const value_type& operator*()const;

Effects: dereferencing a regex_iterator object it yields a const reference to a match_results object, whose members are set as follows:

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Element Value

(*it).size() re.mark_count()

(*it).empty() false

(*it).prefix().first The end of the last match found, or the start of the underlying sequence if this is the ®rst match enumerated

(*it).prefix().last The same as the start of the match found: (*it)[0].first

(*it).prefix().matched True if the pre®x did not match an empty string: (*it).prefix().first != (*it).prefix().second

(*it).suffix().first The same as the end of the match found: (*it)[0].second

(*it).suffix().last The end of the underlying sequence.

(*it).suffix().matched True if the suf®x did not match an empty string: (*it).suffix().first != (*it).suffix().second

(*it)[0].first The start of the sequence of characters that matched the regular expression

(*it)[0].second The end of the sequence of characters that matched the regular expression

(*it)[0].matched true if a full match was found, and false if it was a partial match (found as a result of the match_partial ¯ag being set).

(*it)[n].first For all integers n < (*it).size(), the start of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

(*it)[n].second For all integers n < (*it).size(), the end of the sequence that matched sub-expression n. Alternatively, if sub-expression n did not participate in the match, then last.

(*it)[n].matched For all integers n < (*it).size(), true if sub-expression n participated in the match, false otherwise.

(*it).position(n) For all integers n < (*it).size(), then the distance from the start of the underlying sequence to the start of sub-expression match n.

const value_type* operator->()const;

Effects: returns &(*this).

regex_iterator& operator++();

Effects: moves the iterator to the next match in the underlying sequence, or the end of sequence iterator if none if found. When the last match found matched a zero length string, then the regex_iterator will ®nd the next match as follows: if there exists a non- zero length match that starts at the same location as the last one, then returns it, otherwise starts looking for the next (possibly zero length) match from one position to the right of the last match.

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Returns: *this.

regex_iterator operator++(int);

Effects: constructs a copy result of *this, then calls ++(*this).

Returns: result.

template regex_iterator make_regex_iterator(const charT* p, const basic_regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

template regex_iterator::const_iterator, charT, traits> make_regex_iterator(const std::basic_string& p, const basic_regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

Effects: returns an iterator that enumerates all occurences of expression e in text p using match_flag_type m.

Examples

The following example takes a C++ source ®le and builds up an index of class names, and the location of that class in the ®le.

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#include #include #include #include #include using namespace std;

// purpose: // takes the contents of a file in the form of a string // and searches for all the C++ class definitions, storing // their locations in a map of strings/int©s typedef std::map > map_type; const char* re = // possibly leading whitespace: "^[[:space:]]*" // possible template declaration: "(template[[:space:]]*<[^;:{]+>[[:space:]]*)?" // class or struct: "(class|struct)[[:space:]]*" // leading declspec macros etc: "(" "\\<\\w+\\>" "(" "[[:blank:]]*\$[^)]*\$" ")?" "[[:space:]]*" ")*" // the class name "(\\<\\w*\\>)[[:space:]]*" // template specialisation parameters "(<[^;:{]+>)?[[:space:]]*" // terminate in { or : "(\\{|:[^;\\{()]*\\{)"; boost::regex expression(re); map_type class_index; bool regex_callback(const boost::match_results& what) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: class_index[what[5].str() + what[6].str()] = what.position(5); return true; } void load_file(std::string& s, std::istream& is) { s.erase(); s.reserve(is.rdbuf()->in_avail()); char c; while(is.get(c)) { if(s.capacity() == s.size()) s.reserve(s.capacity() * 3); s.append(1, c); } }

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int main(int argc, const char** argv) { std::string text; for(int i = 1; i < argc; ++i) { cout << "Processing file " << argv[i] << endl; std::ifstream fs(argv[i]); load_file(text, fs); // construct our iterators: boost::sregex_iterator m1(text.begin(), text.end(), expression); boost::sregex_iterator m2; std::for_each(m1, m2, ®ex_callback); // copy results: cout << class_index.size() << " matches found" << endl; map_type::iterator c, d; c = class_index.begin(); d = class_index.end(); while(c != d) { cout << "class \"" << (*c).first << "\" found at index: " << (*c).second << endl; ++c; } class_index.erase(class_index.begin(), class_index.end()); } return 0; } regex_token_iterator

The template class regex_token_iterator is an iterator adapter; that is to say it represents a new view of an existing iterator sequence, by enumerating all the occurrences of a regular expression within that sequence, and presenting one or more character sequence for each match found. Each position enumerated by the iterator is a sub_match object that represents what matched a particular sub-expression within the regular expression. When class regex_token_iterator is used to enumerate a single sub-expression with index -1, then the iterator performs ®eld splitting: that is to say it enumerates one character sequence for each section of the character container sequence that does not match the regular expression speci®ed.

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template ::value_type, class traits = regex_traits > class regex_token_iterator { public: typedef basic_regex regex_type; typedef sub_match value_type; typedef typename iterator_traits::difference_type difference_type; typedef const value_type* pointer; typedef const value_type& reference; typedef std::forward_iterator_tag iterator_category;

regex_token_iterator(); regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, int submatch = 0, match_flag_type m = match_default); regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, const std::vector& submatches, match_flag_type m = match_default); template regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, const int (&submatches)[N], match_flag_type m = match_default); regex_token_iterator(const regex_token_iterator&); regex_token_iterator& operator=(const regex_token_iterator&); bool operator==(const regex_token_iterator&)const; bool operator!=(const regex_token_iterator&)const; const value_type& operator*()const; const value_type* operator->()const; regex_token_iterator& operator++(); regex_token_iterator operator++(int); }; typedef regex_token_iterator cregex_token_iterator; typedef regex_token_iterator sregex_token_iterator; #ifndef BOOST_NO_WREGEX typedef regex_token_iterator wcregex_token_iterator; typedef regex_token_iterator< wsregex_token_iterator; #endif template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, int submatch = 0, regex_constants::match_flag_type m = regex_constants::match_default); template regex_token_iterator::const_iterator, charT, traits> make_regex_token_iterator( const std::basic_string& p, const basic_regex& e, int submatch = 0, regex_constants::match_flag_type m = regex_constants::match_default);

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template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator::const_iterator, charT, traits> make_regex_token_iterator( const std::basic_string& p, const basic_regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator< typename std::basic_string::const_iterator, charT, traits> make_regex_token_iterator( const std::basic_string& p, const basic_regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

Description

regex_token_iterator();

Effects: constructs an end of sequence iterator.

regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, int submatch = 0, match_flag_type m = match_default);

Preconditions: !re.empty(). Object re shall exist for the lifetime of the iterator constructed from it.

Effects: constructs a regex_token_iterator that will enumerate one string for each regular expression match of the expression re found within the sequence [a,b), using match ¯ags m (see match_flag_type). The string enumerated is the sub-expression submatch for each match found; if submatch is -1, then enumerates all the text sequences that did not match the expression re (that is to performs ®eld splitting).

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regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, const std::vector& submatches, match_flag_type m = match_default);

Preconditions: submatches.size() && !re.empty(). Object re shall exist for the lifetime of the iterator constructed from it.

Effects: constructs a regex_token_iterator that will enumerate submatches.size() strings for each regular expression match of the expression re found within the sequence [a,b), using match ¯ags m (see match_flag_type). For each match found one string will be enumerated for each sub-expression index contained within submatches vector; if submatches[0] is -1, then the ®rst string enumerated for each match will be all of the text from end of the last match to the start of the current match, in addition there will be one extra string enumerated when no more matches can be found: from the end of the last match found, to the end of the underlying sequence.

template regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, const int (&submatches)[R], match_flag_type m = match_default);

Preconditions: !re.empty(). Object re shall exist for the lifetime of the iterator constructed from it.

Effects: constructs a regex_token_iterator that will enumerate R strings for each regular expression match of the expression re found within the sequence [a,b), using match ¯ags m (see match_flag_type). For each match found one string will be enumerated for each sub-expression index contained within the submatches array; if submatches[0] is -1, then the ®rst string enumerated for each match will be all of the text from end of the last match to the start of the current match, in addition there will be one extra string enumerated when no more matches can be found: from the end of the last match found, to the end of the underlying sequence.

regex_token_iterator(const regex_token_iterator& that);

Effects: constructs a copy of that.

Postconditions: *this == that.

regex_token_iterator& operator=(const regex_token_iterator& that);

Effects: sets *this to be equal to that.

Postconditions: *this == that.

bool operator==(const regex_token_iterator&)const;

Effects: returns true if *this is the same position as that.

bool operator!=(const regex_token_iterator&)const;

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Effects: returns !(*this == that).

const value_type& operator*()const;

Effects: returns the current character sequence being enumerated.

const value_type* operator->()const;

Effects: returns &(*this).

regex_token_iterator& operator++();

Effects: Moves on to the next character sequence to be enumerated.

Returns: *this.

regex_token_iterator& operator++(int);

Effects: constructs a copy result of *this, then calls ++(*this).

Returns: result.

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template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, int submatch = 0, regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator::const_iterator, charT, traits> make_regex_token_iterator( const std::basic_string& p, const basic_regex& e, int submatch = 0, regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator< typename std::basic_string::const_iterator, charT, traits> make_regex_token_iterator( const std::basic_string& p, const basic_regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template regex_token_iterator make_regex_token_iterator( const charT* p, const basic_regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

Effects: returns a regex_token_iterator that enumerates one sub_match for each value in submatch for each occurrence of regular expression e in string p, matched using match_flag_type m.

Examples

The following example takes a string and splits it into a series of tokens:

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#include #include

using namespace std;

int main(int argc) { string s; do{ if(argc == 1) { cout << "Enter text to split (or \"quit\" to exit): "; getline(cin, s); if(s == "quit") break; } else s = "This is a string of tokens";

boost::regex re("\\s+"); boost::sregex_token_iterator i(s.begin(), s.end(), re, -1); boost::sregex_token_iterator j;

unsigned count = 0; while(i != j) { cout << *i++ << endl; count++; } cout << "There were " << count << " tokens found." << endl;

}while(argc == 1); return 0; }

The following example takes a html ®le and outputs a list of all the linked ®les:

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#include #include #include #include boost::regex e("<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\"", boost::regex::normal | boost::regbase::icase); void load_file(std::string& s, std::istream& is) { s.erase(); // // attempt to grow string buffer to match file size, // this doesn©t always work... s.reserve(is.rdbuf()->in_avail()); char c; while(is.get(c)) { // use logarithmic growth stategy, in case // in_avail (above) returned zero: if(s.capacity() == s.size()) s.reserve(s.capacity() * 3); s.append(1, c); } } int main(int argc, char** argv) { std::string s; int i; for(i = 1; i < argc; ++i) { std::cout << "Findings URL©s in " << argv[i] << ":" << std::endl; s.erase(); std::ifstream is(argv[i]); load_file(s, is); boost::sregex_token_iterator i(s.begin(), s.end(), e, 1); boost::sregex_token_iterator j; while(i != j) { std::cout << *i++ << std::endl; } } // // alternative method: // test the array-literal constructor, and split out the whole // match as well as $1.... // for(i = 1; i < argc; ++i) { std::cout << "Findings URL©s in " << argv[i] << ":" << std::endl; s.erase(); std::ifstream is(argv[i]); load_file(s, is); const int subs[] = {1, 0,}; boost::sregex_token_iterator i(s.begin(), s.end(), e, subs); boost::sregex_token_iterator j; while(i != j) {

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std::cout << *i++ << std::endl; } }

return 0; } bad_expression

Synopsis

#include

The class regex_error de®nes the type of objects thrown as exceptions to report errors during the conversion from a string representing a regular expression to a ®nite state machine.

namespace boost{

class regex_error : public std::runtime_error { public: explicit regex_error(const std::string& s, regex_constants::error_type err, std::ptrdiff_t pos); explicit regex_error(boost::regex_constants::error_type err); boost::regex_constants::error_type code()const; std::ptrdiff_t position()const; };

typedef regex_error bad_pattern; // for backwards compatibility typedef regex_error bad_expression; // for backwards compatibility

} // namespace boost

Description

regex_error(const std::string& s, regex_constants::error_type err, std::ptrdiff_t pos); regex_error(boost::regex_constants::error_type err);

Effects: Constructs an object of class regex_error.

boost::regex_constants::error_type code()const;

Effects: returns the error code that represents parsing error that occurred.

std::ptrdiff_t position()const;

Effects: returns the location in the expression where parsing stopped.

Footnotes: the choice of std::runtime_error as the base class for regex_error is moot; depending upon how the library is used exceptions may be either logic errors (programmer supplied expressions) or run time errors (user supplied expressions). The library previously used bad_pattern and bad_expression for errors, these have been replaced by the single class regex_error to keep the library in synchronization with the Technical Report on C++ Library Extensions.

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Type syntax_option_type is an implementation speci®c bitmask type that controls how a regular expression string is to be interpreted. For convenience note that all the constants listed here, are also duplicated within the scope of class template basic_regex.

namespace std{ namespace regex_constants{

typedef implementation-specific-bitmask-type syntax_option_type;

// these flags are standardized: static const syntax_option_type normal; static const syntax_option_type ECMAScript = normal; static const syntax_option_type JavaScript = normal; static const syntax_option_type JScript = normal; static const syntax_option_type perl = normal; static const syntax_option_type basic; static const syntax_option_type sed = basic; static const syntax_option_type extended; static const syntax_option_type awk; static const syntax_option_type grep; static const syntax_option_type egrep; static const syntax_option_type icase; static const syntax_option_type nosubs; static const syntax_option_type optimize; static const syntax_option_type collate;

// // The remaining options are specific to Boost.Regex: //

// Options common to both Perl and POSIX regular expressions: static const syntax_option_type newline_alt; static const syntax_option_type no_except; static const syntax_option_type save_subexpression_location;

// Perl specific options: static const syntax_option_type no_mod_m; static const syntax_option_type no_mod_s; static const syntax_option_type mod_s; static const syntax_option_type mod_x; static const syntax_option_type no_empty_expressions;

// POSIX extended specific options: static const syntax_option_type no_escape_in_lists; static const syntax_option_type no_bk_refs;

// POSIX basic specific options: static const syntax_option_type no_escape_in_lists; static const syntax_option_type no_char_classes; static const syntax_option_type no_intervals; static const syntax_option_type bk_plus_qm; static const syntax_option_type bk_vbar;

} // namespace regex_constants } // namespace std

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Overview of syntax_option_type

The type syntax_option_type is an implementation speci®c bitmask type (see C++ standard 17.3.2.1.2). Setting its elements has the effects listed in the table below, a valid value of type syntax_option_type will always have exactly one of the elements normal, basic, extended, awk, grep, egrep, sed, literal or perl set.

Note that for convenience all the constants listed here are duplicated within the scope of class template basic_regex, so you can use any of:

boost::regex_constants::constant_name or

boost::regex::constant_name or

boost::wregex::constant_name in an interchangeable manner. Options for Perl Regular Expressions

One of the following must always be set for perl regular expressions:

Element Standardized Effect when set

ECMAScript Yes Speci®es that the grammar recognized by the regular expression engine uses its normal semantics: that is the same as that given in the ECMA-262, ECMAScript Language Speci®cation, Chapter 15 part 10, RegExp (Regular Expression) Objects (FWD.1).

This is functionally identical to the Perl regular expression syntax.

Boost.Regex also recognizes all of the perl-compatible (?...) extensions in this mode.

perl No As above.

normal No As above.

JavaScript No As above.

JScript No As above.

The following options may also be set when using perl-style regular expressions:

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Element Standardized Effect when set icase Yes Speci®es that matching of regular expressions against a character container sequence shall be performed without regard to case. nosubs Yes Speci®es that when a regular expression is matched against a character container sequence, then no sub-expression matches are to be stored in the supplied match_results structure. optimize Yes Speci®es that the regular expression engine should pay more attention to the speed with which regular expressions are matched, and less to the speed with which regular expression objects are constructed. Otherwise it has no detectable effect on the program output. This currently has no effect for Boost.Regex. collate Yes Speci®es that character ranges of the form [a-b] should be locale sensitive. newline_alt No Speci®es that the \n character has the same effect as the alternation operator |. Allows newline separated lists to be used as a list of alternatives. no_except No Prevents basic_regex from throwing an exception when an invalid expression is encountered. no_mod_m No Normally Boost.Regex behaves as if the Perl m-modi®er is on: so the assertions ^ and $ match after and before embedded newlines respectively, setting this ¯ags is equivalent to pre®xing the expression with (?-m). no_mod_s No Normally whether Boost.Regex will match "." against a newline character is determined by the match ¯ag match_dot_not_newline. Specifying this ¯ag is equivalent to pre®xing the expression with (?-s) and therefore causes "." not to match a newline character regardless of whether match_not_dot_newline is set in the match ¯ags.

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Element Standardized Effect when set

mod_s No Normally whether Boost.Regex will match "." against a newline character is determined by the match ¯ag match_dot_not_newline. Specifying this ¯ag is equivalent to pre®xing the expression with (?s) and therefore causes "." to match a newline character regardless of whether match_not_dot_newline is set in the match ¯ags.

mod_x No Turns on the perl x-modi®er: causes unes- caped whitespace in the expression to be ignored.

no_empty_expressions No When set then empty expressions/alternatives are prohibited.

save_subexpression_location No When set then the locations of individual sub-expressions within the original regular expression string can be accessed via the subexpression() member function of basic_regex.

Options for POSIX Extended Regular Expressions

Exactly one of the following must always be set for POSIX extended regular expressions:

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Element Standardized Effect when set

extended Yes Speci®es that the grammar recognized by the regular expression engine is the same as that used by POSIX extended regular expressions in IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base De®nitions and Headers, Section 9, Regular Expressions (FWD.1).

Refer to the POSIX extended regular expression guide for more information.

In addition some perl-style escape sequences are supported (The POSIX standard speci®es that only "special" characters may be escaped, all other escape sequences result in unde®ned behavior).

egrep Yes Speci®es that the grammar recognized by the regular expression engine is the same as that used by POSIX utility grep when given the -E option in IEEE Std 1003.1- 2001, Portable Operating System Interface (POSIX ), Shells and Utilities, Section 4, Utilities, grep (FWD.1).

That is to say, the same as POSIX extended syntax, but with the newline character acting as an alternation character in addition to "|".

awk Yes Speci®es that the grammar recognized by the regular expression engine is the same as that used by POSIX utility awk in IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and Utilities, Section 4, awk (FWD.1).

That is to say: the same as POSIX extended syntax, but with escape sequences in character classes permitted.

In addition some perl-style escape sequences are supported (actually the awk syntax only requires \a \b \t \v \f \n and \r to be recognised, all other Perl-style escape sequences invoke unde®ned behavior according to the POSIX standard, but are in fact recognised by Boost.Regex).

The following options may also be set when using POSIX extended regular expressions:

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Element Standardized Effect when set icase Yes Speci®es that matching of regular expressions against a character container sequence shall be performed without regard to case. nosubs Yes Speci®es that when a regular expression is matched against a character container sequence, then no sub-expression matches are to be stored in the supplied match_results structure. optimize Yes Speci®es that the regular expression engine should pay more attention to the speed with which regular expressions are matched, and less to the speed with which regular expression objects are constructed. Otherwise it has no detectable effect on the program output. This currently has no effect for Boost.Regex. collate Yes Speci®es that character ranges of the form [a-b] should be locale sensitive. This bit is on by default for POSIX-Extended regular expressions, but can be unset to force ranges to be compared by code point only. newline_alt No Speci®es that the \n character has the same effect as the alternation operator |. Allows newline separated lists to be used as a list of alternatives. no_escape_in_lists No When set this makes the escape character ordinary inside lists, so that [\b] would match either ©\© or ©b©. This bit is on by default for POSIX-Extended regular expressions, but can be unset to force escapes to be recognised inside lists. no_bk_refs No When set then backreferences are disabled. This bit is on by default for POSIX- Extended regular expressions, but can be unset to support for backreferences on. no_except No Prevents basic_regex from throwing an exception when an invalid expression is encountered. save_subexpression_location No When set then the locations of individual sub-expressions within the original regular expression string can be accessed via the subexpression() member function of basic_regex.

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Options for POSIX Basic Regular Expressions

Exactly one of the following must always be set for POSIX basic regular expressions:

Element Standardized Effect When Set

basic Yes Speci®es that the grammar recognized by the regular expression engine is the same as that used by POSIX basic regular expressions in IEEE Std 1003.1-2001, Port- able Operating System Interface (POSIX ), Base De®nitions and Headers, Section 9, Regular Expressions (FWD.1).

sed No As Above.

grep Yes Speci®es that the grammar recognized by the regular expression engine is the same as that used by POSIX utility grep in IEEE Std 1003.1-2001, Portable Operat- ing System Interface (POSIX ), Shells and Utilities, Section 4, Utilit\ies, grep (FWD.1).

That is to say, the same as POSIX basic syntax, but with the newline character acting as an alternation character; the expression is treated as a newline separated list of alternatives.

emacs No Speci®es that the grammar recognised is the superset of the POSIX-Basic syntax used by the emacs program.

The following options may also be set when using POSIX basic regular expressions:

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Element Standardized Effect when set icase Yes Speci®es that matching of regular expressions against a character container sequence shall be performed without regard to case. nosubs Yes Speci®es that when a regular expression is matched against a character container sequence, then no sub-expression matches are to be stored in the supplied match_results structure. optimize Yes Speci®es that the regular expression engine should pay more attention to the speed with which regular expressions are matched, and less to the speed with which regular expression objects are constructed. Otherwise it has no detectable effect on the program output. This currently has no effect for Boost.Regex. collate Yes Speci®es that character ranges of the form [a-b] should be locale sensitive. This bit is on by default for POSIX-Basic regular expressions, but can be unset to force ranges to be compared by code point only. newline_alt No Speci®es that the \n character has the same effect as the alternation operator |. Allows newline separated lists to be used as a list of alternatives. This bit is already set, if you use the grep option. no_char_classes No When set then character classes such as [[:alnum:]] are not allowed. no_escape_in_lists No When set this makes the escape character ordinary inside lists, so that [\b] would match either ©\© or ©b©. This bit is on by default for POSIX-basic regular expressions, but can be unset to force escapes to be recognised inside lists. no_intervals No When set then bounded repeats such as a{2,3} are not permitted. bk_plus_qm No When set then \? acts as a zero-or-one repeat operator, and \+ acts as a one-or- more repeat operator. bk_vbar No When set then \| acts as the alternation operator. no_except No Prevents basic_regex from throwing an exception when an invalid expression is encountered.

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Element Standardized Effect when set

Options for Literal Strings

The following must always be set to interpret the expression as a string literal:

Element Standardized Effect when set

literal Yes Treat the string as a literal (no special characters).

The following options may also be combined with the literal ¯ag:

Element Standardized Effect when set

icase Yes Speci®es that matching of regular expressions against a character container sequence shall be performed without regard to case.

optimize Yes Speci®es that the regular expression engine should pay more attention to the speed with which regular expressions are matched, and less to the speed with which regular expression objects are constructed. Otherwise it has no detectable effect on the program output. This currently has no effect for Boost.Regex. match_flag_type

The type match_flag_type is an implementation speci®c bitmask type (see C++ std 17.3.2.1.2) that controls how a regular expression is matched against a character sequence. The behavior of the format ¯ags is described in more detail in the format syntax guide.

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namespace boost{ namespace regex_constants{

typedef implemenation-specific-bitmask-type match_flag_type;

static const match_flag_type match_default = 0; static const match_flag_type match_not_bob; static const match_flag_type match_not_eob; static const match_flag_type match_not_bol; static const match_flag_type match_not_eol; static const match_flag_type match_not_bow; static const match_flag_type match_not_eow; static const match_flag_type match_any; static const match_flag_type match_not_null; static const match_flag_type match_continuous; static const match_flag_type match_partial; static const match_flag_type match_single_line; static const match_flag_type match_prev_avail; static const match_flag_type match_not_dot_newline; static const match_flag_type match_not_dot_null; static const match_flag_type match_posix; static const match_flag_type match_perl; static const match_flag_type match_nosubs; static const match_flag_type match_extra;

static const match_flag_type format_default = 0; static const match_flag_type format_sed; static const match_flag_type format_perl; static const match_flag_type format_literal;

static const match_flag_type format_no_copy; static const match_flag_type format_first_only; static const match_flag_type format_all;

} // namespace regex_constants } // namespace boost

Description

The type match_flag_type is an implementation speci®c bitmask type (see C++ std 17.3.2.1.2). When matching a regular expression against a sequence of characters [®rst, last) then setting its elements has the effects listed in the table below:

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Element Effect if set match_default Speci®es that matching of regular expressions proceeds without any modi®cation of the normal rules used in ECMA-262, ECMAScript Language Speci®cation, Chapter 15 part 10, RegExp (Regular Expression) Objects (FWD.1) match_not_bob Speci®es that the expressions "\A" and "\Á" should not match against the sub-sequence [®rst,®rst). match_not_eob Speci®es that the expressions "\©", "\z" and "\Z" should not match against the sub-sequence [last,last). match_not_bol Speci®es that the expression "^" should not be matched against the sub-sequence [®rst,®rst). match_not_eol Speci®es that the expression "$" should not be matched against the sub-sequence [last,last). match_not_bow Speci®es that the expressions "\<" and "\b" should not be matched against the sub-sequence [®rst,®rst). match_not_eow Speci®es that the expressions "\>" and "\b" should not be matched against the sub-sequence [last,last). match_any Speci®es that if more than one match is possible then any match is an acceptable result: this will still ®nd the leftmost match, but may not ®nd the "best" match at that position. Use this ¯ag if you care about the speed of matching, but don©t care what was matched (only whether there is one or not). match_not_null Speci®es that the expression can not be matched against an empty sequence. match_continuous Speci®es that the expression must match a sub-sequence that begins at ®rst. match_partial Speci®es that if no match can be found, then it is acceptable to return a match [from, last) such that from!= last, if there could exist some longer sequence of characters [from,to) of which [from,last) is a pre®x, and which would result in a full match. This ¯ag is used when matching incomplete or very long texts, see the partial matches documentation for more information. match_extra Instructs the matching engine to retain all available capture information; if a capturing group is repeated then information about every repeat is available via match_results::captures() or sub_match_captures(). match_single_line Equivalent to the inverse of Perl©s m/ modi®er; prevents ^ from matching after an embedded newline character (so that it only matches at the start of the text being matched), and $ from matching before an embedded newline (so that it only matches at the end of the text being matched).

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Element Effect if set match_prev_avail Speci®es that --®rst is a valid iterator position, when this ¯ag is set then the ¯ags match_not_bol and match_not_bow are ignored by the regular expression algorithms (RE.7) and iterators (RE.8). match_not_dot_newline Speci®es that the expression "." does not match a newline character. This is the inverse of Perl©s s/ modi®er. match_not_dot_null Speci®es that the expression "." does not match a character null ©\0©. match_posix Speci®es that the expression should be matched according to the POSIX leftmost-longest rule, regardless of what kind of expression was compiled. Be warned that these rules do not work well with many Perl-speci®c features such as non-greedy repeats. match_perl Speci®es that the expression should be matched according to the Perl matching rules, irrespective of what kind of expression was compiled. match_nosubs Makes the expression behave as if it had no marked subexpressions, no matter how many capturing groups are actually present. The match_results class will only contain information about the overall match, and not any sub-expressions. format_default Speci®es that when a regular expression match is to be replaced by a new string, that the new string is constructed using the rules used by the ECMAScript replace function in ECMA-262, ECMAScript Language Speci®cation, Chapter 15 part 5.4.11 String.prototype.replace. (FWD.1).

This is functionally identical to the Perl format string rules.

In addition during search and replace operations then all non- overlapping occurrences of the regular expression are located and replaced, and sections of the input that did not match the expression, are copied unchanged to the output string. format_sed Speci®es that when a regular expression match is to be replaced by a new string, that the new string is constructed using the rules used by the Unix sed utility in IEEE Std 1003.1-2001, Portable Operating SystemInterface (POSIX ), Shells and Utilities. See also the Sed Format string reference. format_perl Speci®es that when a regular expression match is to be replaced by a new string, that the new string is constructed using the same rules as Perl 5. format_literal Speci®es that when a regular expression match is to be replaced by a new string, that the new string is a literal copy of the replacement text.

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Element Effect if set

format_all Speci®es that all syntax extensions are enabled, including conditional (?ddexpression1:expression2) replacements: see the format string guide for more details.

format_no_copy When speci®ed during a search and replace operation, then sections of the character container sequence being searched that do match the regular expression, are not copied to the output string.

format_®rst_only When speci®ed during a search and replace operation, then only the ®rst occurrence of the regular expression is replaced. error_type

Synopsis

Type error type represents the different types of errors that can be raised by the library when parsing a regular expression.

namespace boost{ namespace regex_constants{

typedef implementation-specific-type error_type;

static const error_type error_collate; static const error_type error_ctype; static const error_type error_escape; static const error_type error_backref; static const error_type error_brack; static const error_type error_paren; static const error_type error_brace; static const error_type error_badbrace; static const error_type error_range; static const error_type error_space; static const error_type error_badrepeat; static const error_type error_complexity; static const error_type error_stack; static const error_type error_bad_pattern;

} // namespace regex_constants } // namespace boost

Description

The type error_type is an implementation-speci®c enumeration type that may take one of the following values:

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Constant Meaning

error_collate An invalid collating element was speci®ed in a [[.name.]] block.

error_ctype An invalid character class name was speci®ed in a [[:name:]] block.

error_escape An invalid or trailing escape was encountered.

error_backref A back-reference to a non-existant marked sub-expression was encountered.

error_brack An invalid character set [...] was encountered.

error_paren Mismatched ©(© and ©)©.

error_brace Mismatched ©{© and ©}©.

error_badbrace Invalid contents of a {...} block.

error_range A character range was invalid, for example [d-a].

error_space Out of memory.

error_badrepeat An attempt to repeat something that can not be repeated - for example a*+

error_complexity The expression became too complex to handle.

error_stack Out of program stack space.

error_bad_pattern Other unspeci®ed errors. regex_traits

namespace boost{

template struct regex_traits : public implementationT { regex_traits() : implementationT() {} };

template struct c_regex_traits;

template class cpp_regex_traits;

template class w32_regex_traits;

} // namespace boost

Description

The class regex_traits is just a thin wrapper around an actual implemention class, which may be one of:

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· c_regex_traits: this class is deprecated, it wraps the C locale, and is used as the default implementation when the platform is not Win32, and the C++ locale is not available.

· cpp_regex_traits: the default traits class for non-Win32 platforms, allows the regex class to be imbued with a std::locale instance.

· w32_regex_traits: the default traits class implementation on Win32 platforms, allows the regex class to be imbued with an LCID.

The default behavior can be altered by de®ning one of the following con®guration macros in boost/regex/user.hpp

· BOOST_REGEX_USE_C_LOCALE: makes c_regex_traits the default.

· BOOST_REGEX_USE_CPP_LOCALE: makes cpp_regex_traits the default.

All these traits classes ful®l the traits class requirements. Interfacing With Non-Standard String Types

The Boost.Regex algorithms and iterators are all iterator-based, with convenience overloads of the algorithms provided that convert standard library string types to iterator pairs internally. If you want to search a non-standard string type then the trick is to convert that string into an iterator pair: so far I haven©t come across any string types that can©t be handled this way, even if they©re not of®cially iterator based. Certainly any string type that provides access to it©s internal buffer, along with it©s length, can be converted into a pair of pointers (which can be used as iterators).

Some non-standard string types are suf®ciently common that wappers have been provided for them already: currently this includes the ICU and MFC string class types. Working With Unicode and ICU String Types

Introduction to using Regex with ICU

The header:

contains the data types and algorithms necessary for working with regular expressions in a Unicode aware environment.

In order to use this header you will need the ICU library, and you will need to have built the Boost.Regex library with ICU support enabled.

The header will enable you to:

· Create regular expressions that treat Unicode strings as sequences of UTF-32 code points.

· Create regular expressions that support various Unicode data properties, including character classi®cation.

· Transparently search Unicode strings that are encoded as either UTF-8, UTF-16 or UTF-32.

Unicode regular expression types

Header provides a regular expression traits class that handles UTF-32 characters:

class icu_regex_traits; and a regular expression type based upon that:

typedef basic_regex u32regex;

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The type u32regex is regular expression type to use for all Unicode regular expressions; internally it uses UTF-32 code points, but can be created from, and used to search, either UTF-8, or UTF-16 encoded strings as well as UTF-32 ones.

The constructors, and assign member functions of u32regex, require UTF-32 encoded strings, but there are a series of overloaded algorithms called make_u32regex which allow regular expressions to be created from UTF-8, UTF-16, or UTF-32 encoded strings:

template u32regex make_u32regex(InputIterator i, InputIterator j, boost::regex_constants::syntax_option_type opt);

Effects: Creates a regular expression object from the iterator sequence [i,j). The character encoding of the sequence is determined based upon sizeof(*i): 1 implies UTF-8, 2 implies UTF-16, and 4 implies UTF-32.

u32regex make_u32regex(const char* p, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the Null-terminated UTF-8 characater sequence p.

u32regex make_u32regex(const unsigned char* p, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the Null-terminated UTF-8 characater sequence p.

u32regex make_u32regex(const wchar_t* p, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the Null-terminated characater sequence p. The character encoding of the sequence is determined based upon sizeof(wchar_t): 1 implies UTF-8, 2 implies UTF-16, and 4 implies UTF-32.

u32regex make_u32regex(const UChar* p, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the Null-terminated UTF-16 characater sequence p.

template u32regex make_u32regex(const std::basic_string& s, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the string s. The character encoding of the string is determined based upon sizeof(C): 1 implies UTF-8, 2 implies UTF-16, and 4 implies UTF-32.

u32regex make_u32regex(const UnicodeString& s, boost::regex_constants::syntax_option_type opt = boost::regex_constants::perl);

Effects: Creates a regular expression object from the UTF-16 encoding string s.

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Unicode Regular Expression Algorithms

The regular expression algorithms regex_match, regex_search and regex_replace all expect that the character sequence upon which they operate, is encoded in the same character encoding as the regular expression object with which they are used. For Unicode regular expressions that behavior is undesirable: while we may want to process the data in UTF-32 "chunks", the actual data is much more likely to encoded as either UTF-8 or UTF-16. Therefore the header provides a series of thin wrappers around these algorithms, called u32regex_match, u32regex_search, and u32regex_replace. These wrappers use iterator- adapters internally to make external UTF-8 or UTF-16 data look as though it©s really a UTF-32 sequence, that can then be passed on to the "real" algorithm. u32regex_match

For each regex_match algorithm de®ned by , then de®nes an overloaded algorithm that takes the same arguments, but which is called u32regex_match, and which will accept UTF-8, UTF-16 or UTF-32 encoded data, as well as an ICU UnicodeString as input.

Example: match a password, encoded in a UTF-16 UnicodeString:

// // Find out if *password* meets our password requirements, // as defined by the regular expression *requirements*. // bool is_valid_password(const UnicodeString& password, const UnicodeString& requirements) { return boost::u32regex_match(password, boost::make_u32regex(requirements)); }

Example: match a UTF-8 encoded ®lename:

// // Extract filename part of a path from a UTF-8 encoded std::string and return the result // as another std::string: // std::string get_filename(const std::string& path) { boost::u32regex r = boost::make_u32regex("(?:\\A|.*\\\\)([^\\\\]+)"); boost::smatch what; if(boost::u32regex_match(path, what, r)) { // extract $1 as a std::string: return what.str(1); } else { throw std::runtime_error("Invalid pathname"); } } u32regex_search

For each regex_search algorithm de®ned by , then de®nes an overloaded algorithm that takes the same arguments, but which is called u32regex_search, and which will accept UTF-8, UTF-16 or UTF-32 encoded data, as well as an ICU UnicodeString as input.

Example: search for a character sequence in a speci®c language block:

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UnicodeString extract_greek(const UnicodeString& text) { // searches through some UTF-16 encoded text for a block encoded in Greek, // this expression is imperfect, but the best we can do for now - searching // for specific scripts is actually pretty hard to do right. // // Here we search for a character sequence that begins with a Greek letter, // and continues with characters that are either not-letters ( [^[:L*:]] ) // or are characters in the Greek character block ( [\\x{370}-\\x{3FF}] ). // boost::u32regex r = boost::make_u32regex( L"[\\x{370}-\\x{3FF}](?:[^[:L*:]]|[\\x{370}-\\x{3FF}])*"); boost::u16match what; if(boost::u32regex_search(text, what, r)) { // extract $0 as a UnicodeString: return UnicodeString(what[0].first, what.length(0)); } else { throw std::runtime_error("No Greek found!"); } } u32regex_replace

For each regex_replace algorithm de®ned by , then de®nes an overloaded algorithm that takes the same arguments, but which is called u32regex_replace, and which will accept UTF-8, UTF-16 or UTF- 32 encoded data, as well as an ICU UnicodeString as input. The input sequence and the format string speci®er passed to the algorithm, can be encoded independently (for example one can be UTF-8, the other in UTF-16), but the result string / output iterator argument must use the same character encoding as the text being searched.

Example: Credit card number reformatting:

// // Take a credit card number as a string of digits, // and reformat it as a human readable string with "-" // separating each group of four digit;, // note that we©re mixing a UTF-32 regex, with a UTF-16 // string and a UTF-8 format specifier, and it still all // just works: // const boost::u32regex e = boost::make_u32regex( "\\A(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})\\z"); const char* human_format = "$1-$2-$3-$4";

UnicodeString human_readable_card_number(const UnicodeString& s) { return boost::u32regex_replace(s, e, human_format); }

Unicode Aware Regex Iterators u32regex_iterator

Type u32regex_iterator is in all respects the same as regex_iterator except that since the regular expression type is always u32regex it only takes one template parameter (the iterator type). It also calls u32regex_search internally, allowing it to interface correctly with UTF-8, UTF-16, and UTF-32 data:

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template class u32regex_iterator { // for members see regex_iterator };

typedef u32regex_iterator utf8regex_iterator; typedef u32regex_iterator utf16regex_iterator; typedef u32regex_iterator utf32regex_iterator;

In order to simplify the construction of a u32regex_iterator from a string, there are a series of non-member helper functions called make_u32regex_iterator:

u32regex_iterator make_u32regex_iterator(const char* s, const u32regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_iterator make_u32regex_iterator(const wchar_t* s, const u32regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_iterator make_u32regex_iterator(const UChar* s, const u32regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_iterator::const_iterator> make_u32regex_iterator(const std::basic_string& s, const u32regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_iterator make_u32regex_iterator(const UnicodeString& s, const u32regex& e, regex_constants::match_flag_type m = regex_constants::match_default);

Each of these overloads returns an iterator that enumerates all occurrences of expression e, in text s, using match_¯ags m.

Example: search for international currency symbols, along with their associated numeric value:

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void enumerate_currencies(const std::string& text) { // enumerate and print all the currency symbols, along // with any associated numeric values: const char* re = "([[:Sc:]][[:Cf:][:Cc:][:Z*:]]*)?" "([[:Nd:]]+(?:[[:Po:]][[:Nd:]]+)?)?" "(?(1)" "|(?(2)" "[[:Cf:][:Cc:][:Z*:]]*" ")" "[[:Sc:]]" ")"; boost::u32regex r = boost::make_u32regex(re); boost::u32regex_iterator i(boost::make_u32regex_iterator(text, r)), j; while(i != j) { std::cout << (*i)[0] << std::endl; ++i; } }

Calling

enumerate_currencies(" $100.23 or £198.12 ");

Yields the output:

$100.23 £198.12

Provided of course that the input is encoded as UTF-8. u32regex_token_iterator

Type u32regex_token_iterator is in all respects the same as regex_token_iterator except that since the regular expression type is always u32regex it only takes one template parameter (the iterator type). It also calls u32regex_search internally, allowing it to interface correctly with UTF-8, UTF-16, and UTF-32 data:

template class u32regex_token_iterator { // for members see regex_token_iterator };

typedef u32regex_token_iterator utf8regex_token_iterator; typedef u32regex_token_iterator utf16regex_token_iterator; typedef u32regex_token_iterator utf32regex_token_iterator;

In order to simplify the construction of a u32regex_token_iterator from a string, there are a series of non-member helper functions called make_u32regex_token_iterator:

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u32regex_token_iterator make_u32regex_token_iterator( const char* s, const u32regex& e, int sub, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const wchar_t* s, const u32regex& e, int sub, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const UChar* s, const u32regex& e, int sub, regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator::const_iterator> make_u32regex_token_iterator( const std::basic_string& s, const u32regex& e, int sub, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const UnicodeString& s, const u32regex& e, int sub, regex_constants::match_flag_type m = regex_constants::match_default);

Each of these overloads returns an iterator that enumerates all occurrences of marked sub-expression sub in regular expression e, found in text s, using match_¯ags m.

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template u32regex_token_iterator make_u32regex_token_iterator( const char* p, const u32regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator make_u32regex_token_iterator( const wchar_t* p, const u32regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator make_u32regex_token_iterator( const UChar* p, const u32regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator::const_iterator> make_u32regex_token_iterator( const std::basic_string& p, const u32regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator make_u32regex_token_iterator( const UnicodeString& s, const u32regex& e, const int (&submatch)[N], regex_constants::match_flag_type m = regex_constants::match_default);

Each of these overloads returns an iterator that enumerates one sub-expression for each submatch in regular expression e, found in text s, using match_¯ags m.

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u32regex_token_iterator make_u32regex_token_iterator( const char* p, const u32regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const wchar_t* p, const u32regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const UChar* p, const u32regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

template u32regex_token_iterator::const_iterator> make_u32regex_token_iterator( const std::basic_string& p, const u32regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

u32regex_token_iterator make_u32regex_token_iterator( const UnicodeString& s, const u32regex& e, const std::vector& submatch, regex_constants::match_flag_type m = regex_constants::match_default);

Each of these overloads returns an iterator that enumerates one sub-expression for each submatch in regular expression e, found in text s, using match_¯ags m.

Example: search for international currency symbols, along with their associated numeric value:

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void enumerate_currencies2(const std::string& text) { // enumerate and print all the currency symbols, along // with any associated numeric values: const char* re = "([[:Sc:]][[:Cf:][:Cc:][:Z*:]]*)?" "([[:Nd:]]+(?:[[:Po:]][[:Nd:]]+)?)?" "(?(1)" "|(?(2)" "[[:Cf:][:Cc:][:Z*:]]*" ")" "[[:Sc:]]" ")"; boost::u32regex r = boost::make_u32regex(re); boost::u32regex_token_iterator i(boost::make_u32regex_token_iterator(text, r, 1)), j; while(i != j) { std::cout << *i << std::endl; ++i; } }

Using Boost Regex With MFC Strings

Introduction to Boost.Regex and MFC Strings

The header provides Boost.Regex support for MFC string types: note that this support requires Visual Studio .NET (Visual C++ 7) or later, where all of the MFC and ATL string types are based around the CSimpleStringT class template.

In the following documentation, whenever you see CSimpleStringT, then you can substitute any of the following MFC/ATL types (all of which inherit from CSimpleStringT):

CString CStringA CStringW CAtlString CAtlStringA CAtlStringW CStringT CFixedStringT CSimpleStringT

Regex Types Used With MFC Strings

typedef basic_regex tregex; typedef match_results tmatch; typedef regex_iterator tregex_iterator; typedef regex_token_iterator tregex_token_iterator;

If you are working with explicitly narrow or wide characters rather than TCHAR, then use the regular Boost.Regex types regex and wregex instead.

Regular Expression Creation From an MFC String

The following helper function is available to assist in the creation of a regular expression from an MFC/ATL string type:

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template basic_regex make_regex(const ATL::CSimpleStringT& s, ::boost::regex_constants::syntax_option_type f = boost::regex_constants::normal);

Effects: returns basic_regex(s.GetString(), s.GetString() + s.GetLength(), f);

Overloaded Algorithms For MFC String Types

For each regular expression algorithm that©s overloaded for a std::basic_string argument, there is also one overloaded for the MFC/ATL string types. These algorithm signatures all look a lot more complex than they actually are, but for completeness here they are anyway: regex_match

There are two overloads, the ®rst reports what matched in a match_results structure, the second does not.

All the usual caveats for regex_match apply, in particular the algorithm will only report a successful match if all of the input text matches the expression, if this isn©t what you want then use regex_search instead.

template bool regex_match( const ATL::CSimpleStringT& s, match_results& what, const basic_regex& e, boost::regex_constants::match_flag_type f = boost::regex_constants::match_default);

Effects: returns ::boost::regex_match(s.GetString(), s.GetString() + s.GetLength(), what, e, f);

Example:

// // Extract filename part of a path from a CString and return the result // as another CString: // CString get_filename(const CString& path) { boost::tregex r(__T("(?:\\A|.*\\\\)([^\\\\]+)")); boost::tmatch what; if(boost::regex_match(path, what, r)) { // extract $1 as a CString: return CString(what[1].first, what.length(1)); } else { throw std::runtime_error("Invalid pathname"); } } regex_match (second overload)

template bool regex_match( const ATL::CSimpleStringT& s, const basic_regex& e, boost::regex_constants::match_flag_type f = boost::regex_constants::match_default)

Effects: returns ::boost::regex_match(s.GetString(), s.GetString() + s.GetLength(), e, f);

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Example:

// // Find out if *password* meets our password requirements, // as defined by the regular expression *requirements*. // bool is_valid_password(const CString& password, const CString& requirements) { return boost::regex_match(password, boost::make_regex(requirements)); } regex_search

There are two additional overloads for regex_search, the ®rst reports what matched the second does not:

template bool regex_search(const ATL::CSimpleStringT& s, match_results& what, const basic_regex& e, boost::regex_constants::match_flag_type f = boost::regex_constants::match_de↵ fault)

Effects: returns ::boost::regex_search(s.GetString(), s.GetString() + s.GetLength(), what, e, f);

Example: Postcode extraction from an address string.

CString extract_postcode(const CString& address) { // searches throw address for a UK postcode and returns the result, // the expression used is by Phil A. on www.regxlib.com: boost::tregex r(__T("^(([A-Z]{1,2}[0-9]{1,2})|([A-Z]{1,2}[0-9][A-Z]))\\s?([0-9][A-Z]{2})$")); boost::tmatch what; if(boost::regex_search(address, what, r)) { // extract $0 as a CString: return CString(what[0].first, what.length()); } else { throw std::runtime_error("No postcode found"); } } regex_search (second overload)

template inline bool regex_search(const ATL::CSimpleStringT& s, const basic_regex& e, boost::regex_constants::match_flag_type f = boost::regex_constants::match_default)

Effects: returns ::boost::regex_search(s.GetString(), s.GetString() + s.GetLength(), e, f); regex_replace

There are two additional overloads for regex_replace, the ®rst sends output to an output iterator, while the second creates a new string

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template OutputIterator regex_replace(OutputIterator out, BidirectionalIterator first, BidirectionalIterator last, const basic_regex& e, const ATL::CSimpleStringT& fmt, match_flag_type flags = match_default)

Effects: returns ::boost::regex_replace(out, first, last, e, fmt.GetString(), flags);

template ATL::CSimpleStringT regex_replace(const ATL::CSimpleStringT& s, const basic_regex& e, const ATL::CSimpleStringT& fmt, match_flag_type flags = match_default)

Effects: returns a new string created using regex_replace, and the same memory manager as string s.

Example:

// // Take a credit card number as a string of digits, // and reformat it as a human readable string with "-" // separating each group of four digits: // const boost::tregex e(__T("\\A(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})\\z")); const CString human_format = __T("$1-$2-$3-$4");

CString human_readable_card_number(const CString& s) { return boost::regex_replace(s, e, human_format); }

Iterating Over the Matches Within An MFC String

The following helper functions are provided to ease the conversion from an MFC/ATL string to a regex_iterator or regex_token_iterator: regex_iterator creation helper

template regex_iterator make_regex_iterator( const ATL::CSimpleStringT& s, const basic_regex& e, ::boost::regex_constants::match_flag_type f = boost::regex_constants::match_default);

Effects: returns regex_iterator(s.GetString(), s.GetString() + s.GetLength(), e, f);

Example:

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void enumerate_links(const CString& html) { // enumerate and print all the links in some HTML text, // the expression used is by Andew Lee on www.regxlib.com: boost::tregex r( __T("href=[\"\©]((http:\\/\\/|\\.\\/|\\/)?\\w+" "(\\.\\w+)*(\\/\\w+(\\.\\w+)?)*" "(\\/|\\?\\w*=\\w*(&\\w*=\\w*)*)?)[\"\©]")); boost::tregex_iterator i(boost::make_regex_iterator(html, r)), j; while(i != j) { std::cout << (*i)[1] << std::endl; ++i; } } regex_token_iterator creation helpers

template regex_token_iterator make_regex_token_iterator( const ATL::CSimpleStringT& s, const basic_regex& e, int sub = 0, ::boost::regex_constants::match_flag_type f = boost::regex_constants::match_default);

Effects: returns regex_token_iterator(s.GetString(), s.GetString() + s.GetLength(), e, sub, f);

template regex_token_iterator make_regex_token_iterator( const ATL::CSimpleStringT& s, const basic_regex& e, const std::vector& subs, ::boost::regex_constants::match_flag_type f = boost::regex_constants::match_default);

Effects: returns regex_token_iterator(s.GetString(), s.GetString() + s.GetLength(), e, subs, f);

template regex_token_iterator make_regex_token_iterator( const ATL::CSimpleStringT& s, const basic_regex& e, const int (& subs)[N], ::boost::regex_constants::match_flag_type f = boost::regex_constants::match_default);

Effects: returns regex_token_iterator(s.GetString(), s.GetString() + s.GetLength(), e, subs, f);

Example:

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void enumerate_links2(const CString& html) { // enumerate and print all the links in some HTML text, // the expression used is by Andew Lee on www.regxlib.com: boost::tregex r( __T("href=[\"\©]((http:\\/\\/|\\.\\/|\\/)?\\w+" "(\\.\\w+)*(\\/\\w+(\\.\\w+)?)*" "(\\/|\\?\\w*=\\w*(&\\w*=\\w*)*)?)[\"\©]")); boost::tregex_token_iterator i(boost::make_regex_token_iterator(html, r, 1)), j; while(i != j) { std::cout << *i << std::endl; ++i; } }

Note

this is an abridged reference to the POSIX API functions, these are provided for compatibility with other libraries, rather than as an API to be used in new code (unless you need access from a language other than C++). This version of these functions should also happily coexist with other versions, as the names used are macros that expand to the actual function names.

#include or:

#include

The following functions are available for users who need a POSIX compatible C library, they are available in both Unicode and narrow character versions, the standard POSIX API names are macros that expand to one version or the other depending upon whether UNICODE is de®ned or not.

Important

Note that all the symbols de®ned here are enclosed inside namespace boost when used in C++ programs, unless you use #include instead - in which case the symbols are still de®ned in namespace boost, but are made available in the global namespace as well.

The functions are de®ned as:

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extern "C" {

struct regex_tA; struct regex_tW;

int regcompA(regex_tA*, const char*, int); unsigned int regerrorA(int, const regex_tA*, char*, unsigned int); int regexecA(const regex_tA*, const char*, unsigned int, regmatch_t*, int); void regfreeA(regex_tA*);

int regcompW(regex_tW*, const wchar_t*, int); unsigned int regerrorW(int, const regex_tW*, wchar_t*, unsigned int); int regexecW(const regex_tW*, const wchar_t*, unsigned int, regmatch_t*, int); void regfreeW(regex_tW*);

#ifdef UNICODE #define regcomp regcompW #define regerror regerrorW #define regexec regexecW #define regfree regfreeW #define regex_t regex_tW #else #define regcomp regcompA #define regerror regerrorA #define regexec regexecA #define regfree regfreeA #define regex_t regex_tA #endif }

All the functions operate on structure regex_t, which exposes two public members:

Member Meaning

unsigned int re_nsub This is ®lled in by regcomp and indicates the number of sub- expressions contained in the regular expression.

const TCHAR* re_endp Points to the end of the expression to compile when the ¯ag REG_PEND is set.

Note

regex_t is actually a #define - it is either regex_tA or regex_tW depending upon whether UNICODE is de®ned or not, TCHAR is either char or wchar_t again depending upon the macro UNICODE. regcomp regcomp takes a pointer to a regex_t, a pointer to the expression to compile and a ¯ags parameter which can be a combination of:

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Flag Meaning

REG_EXTENDED Compiles modern regular expressions. Equivalent to regbase::char_classes | regbase::intervals | regbase::bk_refs.

REG_NOSPEC All characters are ordinary, the expression is a literal string.

REG_ICASE Compiles for matching that ignores character case.

REG_NOSUB Has no effect in this library.

REG_NEWLINE When this ¯ag is set a dot does not match the newline character.

REG_PEND When this ¯ag is set the re_endp parameter of the regex_t structure must point to the end of the regular expression to compile.

REG_NOCOLLATE When this ¯ag is set then locale dependent collation for character ranges is turned off.

REG_ESCAPE_IN_LISTS When this ¯ag is set, then escape sequences are permitted in bracket expressions (character sets).

REG_NEWLINE_ALT When this ¯ag is set then the newline character is equivalent to the alternation operator |.

REG_PERL Compiles Perl like regular expressions.

REG_AWK A shortcut for awk-like behavior: REG_EXTENDED | REG_ES- CAPE_IN_LISTS

REG_GREP A shortcut for grep like behavior: REG_BASIC | REG_NEWLINE_ALT

REG_EGREP A shortcut for egrep like behavior: REG_EXTENDED | REG_NEWLINE_ALT regerror regerror takes the following parameters, it maps an error code to a human readable string:

Parameter Meaning

int code The error code.

const regex_t* e The regular expression (can be null).

char* buf The buffer to ®ll in with the error message.

unsigned int buf_size The length of buf.

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If the error code is OR©ed with REG_ITOA then the message that results is the printable name of the code rather than a message, for example "REG_BADPAT". If the code is REG_ATIO then e must not be null and e->re_pend must point to the printable name of an error code, the return value is then the value of the error code. For any other value of code, the return value is the number of characters in the error message, if the return value is greater than or equal to buf_size then regerror will have to be called again with a larger buffer. regexec regexec ®nds the ®rst occurrence of expression e within string buf. If len is non-zero then *m is ®lled in with what matched the regular expression, m[0] contains what matched the whole string, m[1] the ®rst sub-expression etc, see regmatch_t in the header ®le declaration for more details. The e¯ags parameter can be a combination of:

Flag Meaning

REG_NOTBOL Parameter buf does not represent the start of a line.

REG_NOTEOL Parameter buf does not terminate at the end of a line.

REG_STARTEND The string searched starts at buf + pmatch[0].rm_so and ends at buf + pmatch[0].rm_eo. regfree regfree frees all the memory that was allocated by regcomp. Concepts charT Requirements

Type charT used a template argument to class template basic_regex, must have a trivial default constructor, copy constructor, assignment operator, and destructor. In addition the following requirements must be met for objects; c of type charT, c1 and c2 of type charT const, and i of type int:

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Expression Return type Assertion / Note / Pre- / Post-condition

charT c charT Default constructor (must be trivial).

charT c(c1) charT Copy constructor (must be trivial).

c1 = c2 charT Assignment operator (must be trivial).

c1 == c2 bool true if c1 has the same value as c2.

c1 != c2 bool true if c1 and c2 are not equal.

c1 < c2 bool true if the value of c1 is less than c2.

c1 > c2 bool true if the value of c1 is greater than c2.

c1 <= c2 bool true if c1 is less than or equal to c2.

c1 >= c2 bool true if c1 is greater than or equal to c2.

intmax_t i = c1 int charT must be convertible to an integral type.

Note: type charT is not required to support this operation, if the traits class used supports the full Boost-speci®c interface, rather than the minimal standardised-interface (see traits class requirements below).

charT c(i); charT charT must be constructable from an integral type.

Traits Class Requirements

There are two sets of requirements for the traits template argument to basic_regex: a mininal interface (which is part of the regex standardization proposal), and an optional Boost-speci®c enhanced interface.

Minimal requirements.

In the following table X denotes a traits class de®ning types and functions for the character container type charT; u is an object of type X; v is an object of type const X; p is a value of type const charT*; I1 and I2 are Input Iterators; c is a value of type const charT; s is an object of type X::string_type; cs is an object of type const X::string_type; b is a value of type bool; I is a value of type int; F1 and F2 are values of type const charT*; and loc is an object of type X::locale_type.

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Expression Return type Assertion / Note Pre / Post condition

X::char_type charT The character container type used in the implementation of class template ba- sic_regex.

X::string_type std::basic_string or std::vector

X::locale_type Implementation de®ned A copy constructible type that represents the locale used by the traits class.

X::char_class_type Implementation de®ned A bitmask type representing a particular character classi®cation. Multiple values of this type can be bitwise-or©ed together to obtain a new valid value.

X::length(p) X::size_type Yields the smallest i such that p[i] == 0. Complexity is linear in i. v.translate(c) X::char_type Returns a character such that for any character d that is to be considered equivalent to c then v.translate(c) == v.translate(d). v.translate_nocase(c) X::char_type For all characters C that are to be considered equivalent to c when comparisons are to be performed without regard to case, then v.translate_nocase(c) == v.translate_nocase(C). v.transform(F1, F2) X::string_type Returns a sort key for the character sequence designated by the iterator range [F1, F2) such that if the character sequence [G1, G2) sorts before the character sequence [H1, H2) then v.transform(G1, G2) < v.transform(H1, H2). v.transform_primary(F1, F2) X::string_type Returns a sort key for the character sequence designated by the iterator range [F1, F2) such that if the character sequence [G1, G2) sorts before the character sequence [H1, H2) when character case is not considered then v.trans- form_primary(G1, G2) < v.trans- form_primary(H1, H2).

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Expression Return type Assertion / Note Pre / Post condition

v.lookup_classname(F1, F2) X::char_class_type Converts the character sequence designated by the iterator range [F1,F2) into a bitmask type that can subsequently be passed to isctype. Values returned from lookup_classname can be safely bitwise or©ed together. Returns 0 if the character sequence is not the name of a character class recognized by X. The value returned shall be independent of the case of the characters in the sequence.

v.lookup_collatename(F1, F2) X::string_type Returns a sequence of characters that represents the collating element consisting of the character sequence designated by the iterator range [F1, F2). Returns an empty string if the character sequence is not a valid collating element.

v.isctype(c, v.lookup_classname (F1, F2)) bool Returns true if character c is a member of the character class designated by the iterator range [F1, F2), false otherwise.

v.value(c, I) int Returns the value represented by the digit c in base I if the character c is a valid digit in base I; otherwise returns -1. [Note: the value of I will only be 8, 10, or 16. -end note]

u.imbue(loc) X::locale_type Imbues u with the locale loc, returns the previous locale used by u if any.

v.getloc() X::locale_type Returns the current locale used by v if any.

Additional Optional Requirements

The following additional requirements are strictly optional, however in order for basic_regex to take advantage of these additional interfaces, all of the following requirements must be met; basic_regex will detect the presence or absense of the member boost_extensions_tag and con®gure itself appropriately.

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Expression Result Assertion / Note Pre / Post condition

X::boost_extensions_tag An unspeci®ed type. When present, all of the extensions listed in this table must be present.

v.syntax_type(c) regex_constants::syntax_type Returns a symbolic value of type regex_constants::syntax_type that signi- ®es the meaning of character c within the regular expression grammar.

v.escape_syntax_type(c) regex_constants::escape_syntax_type Returns a symbolic value of type regex_constants::escape_syntax_type, that signi®es the meaning of character c within the regular expression grammar, when c has been preceded by an escape character. Precondition: if b is the character preceding c in the expression being parsed then: v.syntax_type(b) == syntax_es- cape

v.translate(c, b) X::char_type Returns a character d such that: for any character d that is to be considered equivalent to c then v.translate(c,false)==v.translate(d,false). Likewise for all characters C that are to be considered equivalent to c when comparisons are to be performed without regard to case, then v.translate(c,true)==v.translate(C,true).

v.toi(I1, I2, i) An integer type capable of holding either Behaves as follows: if p == q or if *p is a charT or an int. not a digit character then returns -1. Oth- erwise performs formatted numeric input on the sequence [p,q) and returns the result as an int. Postcondition: either p == q or *p is a non-digit character.

v.error_string(I) std::string Returns a human readable error string for the error condition i, where i is one of the values enumerated by type regex_con- stants::error_type. If the value I is not recognized then returns the string "Un- known error" or a localized equivalent.

v.tolower(c) X::char_type Converts c to lower case, used for Perl- style \l and \L formating operations.

v.toupper(c) X::char_type Converts c to upper case, used for Perl- style \u and \U formating operations.

Iterator Requirements

The regular expression algorithms (and iterators) take all require a Bidirectional-Iterator.

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Deprecated Interfaces regex_format (Deprecated)

The algorithm regex_format is deprecated; new code should use match_results<>::format instead. Existing code will continue to compile, the following documentation is taken from the previous version of Boost.Regex and will not be further updated:

Algorithm regex_format

#include

The algorithm regex_format takes the results of a match and creates a new string based upon a format string, regex_format can be used for search and replace operations:

template OutputIterator regex_format(OutputIterator out, const match_results& m, Formatter fmt, match_flag_type flags = 0);

The library also de®nes the following convenience variation of regex_format, which returns the result directly as a string, rather than outputting to an iterator.

Note

This version may not be available, or may be available in a more limited form, depending upon your compilers capabilities

template std::basic_string regex_format (const match_results& m, Formatter fmt, match_flag_type flags = 0);

Parameters to the main version of the function are passed as follows:

Parameter Description

OutputIterator out An output iterator type, the output string is sent to this iterator. Typically this would be a std::ostream_iterator.

const match_results& m An instance of match_results obtained from one of the matching algorithms above, and denoting what matched.

Formatter fmt Either a format string that determines how the match is trans- formed into the new string, or a functor that computes the new string from m - see match_results<>::format.

unsigned flags Optional ¯ags which describe how the format string is to be interpreted.

Format ¯ags are described under match_flag_type.

The format string syntax (and available options) is described more fully under format strings.

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The algorithm regex_grep is deprecated in favor of regex_iterator which provides a more convenient and standard library friendly interface.

The following documentation is taken unchanged from the previous boost release, and will not be updated in future.

#include regex_grep allows you to search through a bidirectional-iterator range and locate all the (non-overlapping) matches with a given regular expression. The function is declared as:

template unsigned int regex_grep(Predicate foo, iterator first, iterator last, const basic_regex& e, boost::match_flag_type flags = match_default)

The library also de®nes the following convenience versions, which take either a const charT*, or a const std::ba- sic_string<>& in place of a pair of iterators.

template unsigned int regex_grep(Predicate foo, const charT* str, const basic_regex& e, boost::match_flag_type flags = match_default);

template unsigned int regex_grep(Predicate foo, const std::basic_string& s, const basic_regex& e, boost::match_flag_type flags = match_default);

The parameters for the primary version of regex_grep have the following meanings: foo: A predicate function object or function pointer, see below for more information.

®rst: The start of the range to search. last: The end of the range to search. e: The regular expression to search for.

¯ags: The ¯ags that determine how matching is carried out, one of the match_¯ags enumerators.

The algorithm ®nds all of the non-overlapping matches of the expression e, for each match it ®lls a match_results structure, which contains information on what matched, and calls the predicate foo, passing the match_results as a single argument. If the predicate returns true, then the grep operation continues, otherwise it terminates without searching for further matches. The function returns the number of matches found.

The general form of the predicate is:

struct grep_predicate { bool operator()(const match_results& m); };

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For example the regular expression "a*b" would ®nd one match in the string "aaaaab" and two in the string "aaabb".

Remember this algorithm can be used for a lot more than implementing a version of grep, the predicate can be and do anything that you want, grep utilities would output the results to the screen, another program could index a ®le based on a regular expression and store a set of bookmarks in a list, or a text ®le conversion utility would output to ®le. The results of one regex_grep can even be chained into another regex_grep to create recursive parsers.

The algorithm may throw std::runtime_error if the complexity of matching the expression against an N character string begins to exceed O(N2), or if the program runs out of stack space while matching the expression (if Boost.Regex is con®gured in recursive mode), or if the matcher exhausts it©s permitted memory allocation (if Boost.Regex is con®gured in non-recursive mode).

Example: convert the example from regex_search to use regex_grep instead:

#include #include #include

// IndexClasses: // takes the contents of a file in the form of a string // and searches for all the C++ class definitions, storing // their locations in a map of strings/int©s typedef std::map > map_type;

const char* re = // possibly leading whitespace: "^[[:space:]]*" // possible template declaration: "(template[[:space:]]*<[^;:{]+>[[:space:]]*)?" // class or struct: "(class|struct)[[:space:]]*" // leading declspec macros etc: "(" "\\<\\w+\\>" "(" "[[:blank:]]*\$[^)]*\$" ")?" "[[:space:]]*" ")*" // the class name "(\\<\\w*\\>)[[:space:]]*" // template specialisation parameters "(<[^;:{]+>)?[[:space:]]*" // terminate in { or : "(\\{|:[^;\\{()]*\\{)";

boost::regex expression(re); class IndexClassesPred { map_type& m; std::string::const_iterator base; public: IndexClassesPred(map_type& a, std::string::const_iterator b) : m(a), base(b) {} bool operator()(const smatch& what) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: m[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] = what[5].first - base; return true; }

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}; void IndexClasses(map_type& m, const std::string& file) { std::string::const_iterator start, end; start = file.begin(); end = file.end(); regex_grep(IndexClassesPred(m, start), start, end, expression); }

Example: Use regex_grep to call a global callback function:

#include #include #include

boost::regex expression(re); map_type class_index; std::string::const_iterator base;

bool grep_callback(const boost::smatch& what) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: class_in↵ dex[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] = what[5].first - base; return true; } void IndexClasses(const std::string& file) {

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std::string::const_iterator start, end; start = file.begin(); end = file.end(); base = start; regex_grep(grep_callback, start, end, expression, match_default); }

Example: use regex_grep to call a class member function, use the standard library adapters std::mem_fun and std::bind1st to convert the member function into a predicate:

#include #include #include #include // purpose: // takes the contents of a file in the form of a string // and searches for all the C++ class definitions, storing // their locations in a map of strings/int©s

typedef std::map > map_type; class class_index { boost::regex expression; map_type index; std::string::const_iterator base; bool grep_callback(boost::smatch what); public: void IndexClasses(const std::string& file); class_index() : index(), expression("^(template[[:space:]]*<[^;:{]+>[[:space:]]*)?" "(class|struct)[[:space:]]*(\\<\\w+\\>([[:blank:]]*\$[^)]*\$)?" "[[:space:]]*)*(\\<\\w*\\>)[[:space:]]*(<[^;:{]+>[[:space:]]*)?" "(\\{|:[^;\\{()]*\\{)" ){} }; bool class_index::grep_callback(boost::smatch what) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: index[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] = what[5].first - base; return true; }

void class_index::IndexClasses(const std::string& file) { std::string::const_iterator start, end; start = file.begin(); end = file.end(); base = start; regex_grep(std::bind1st(std::mem_fun(&class_index::grep_callback), this), start, end, expression); }

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typedef std::map > map_type; class class_index { boost::regex expression; map_type index; std::string::const_iterator base; typedef boost::smatch arg_type; bool grep_callback(const arg_type& what); public: typedef bool (__closure* grep_callback_type)(const arg_type&); void IndexClasses(const std::string& file); class_index() : index(), expression("^(template[[:space:]]*<[^;:{]+>[[:space:]]*)?" "(class|struct)[[:space:]]*(\\<\\w+\\>([[:blank:]]*\$[^)]*\$)?" "[[:space:]]*)*(\\<\\w*\\>)[[:space:]]*(<[^;:{]+>[[:space:]]*)?" "(\\{|:[^;\\{()]*\\{)" ){} };

bool class_index::grep_callback(const arg_type& what) { // what[0] contains the whole string // what[5] contains the class name. // what[6] contains the template specialisation if any. // add class name and position to map: index[std::string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second)] = what[5].first - base; return true; }

void class_index::IndexClasses(const std::string& file) { std::string::const_iterator start, end; start = file.begin(); end = file.end(); base = start; class_index::grep_callback_type cl = &(this->grep_callback); regex_grep(cl, start, end, expression); } regex_split (deprecated)

The algorithm regex_split has been deprecated in favor of the iterator regex_token_iterator which has a more ¯exible and powerful interface, as well as following the more usual standard library "pull" rather than "push" semantics.

Code which uses regex_split will continue to compile, the following documentation is taken from a previous Boost.Regex version:

#include

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Algorithm regex_split performs a similar operation to the perl split operation, and comes in three overloaded forms:

template std::size_t regex_split(OutputIterator out, std::basic_string& s, const basic_regex& e, boost::match_flag_type flags, std::size_t max_split);

template std::size_t regex_split(OutputIterator out, std::basic_string& s, const basic_regex& e, boost::match_flag_type flags = match_default);

template std::size_t regex_split(OutputIterator out, std::basic_string& s);

Effects: Each version of the algorithm takes an output-iterator for output, and a string for input. If the expression contains no marked sub-expressions, then the algorithm writes one string onto the output-iterator for each section of input that does not match the expression. If the expression does contain marked sub-expressions, then each time a match is found, one string for each marked sub-expression will be written to the output-iterator. No more than max_split strings will be written to the output-iterator. Before returning, all the input processed will be deleted from the string s (if max_split is not reached then all of s will be deleted). Returns the number of strings written to the output-iterator. If the parameter max_split is not speci®ed then it defaults to UINT_MAX. If no expression is speci®ed, then it defaults to "\s+", and splitting occurs on whitespace.

Example: the following function will split the input string into a series of tokens, and remove each token from the string s:

unsigned tokenise(std::list& l, std::string& s) { return boost::regex_split(std::back_inserter(l), s); }

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#include #include #include #include

boost::regex e("<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\"", boost::regbase::normal | boost::regbase::icase);

void load_file(std::string& s, std::istream& is) { s.erase(); // // attempt to grow string buffer to match file size, // this doesn©t always work... s.reserve(is.rdbuf()->in_avail()); char c; while(is.get(c)) { // use logarithmic growth stategy, in case // in_avail (above) returned zero: if(s.capacity() == s.size()) s.reserve(s.capacity() * 3); s.append(1, c); } }

int main(int argc, char** argv) { std::string s; std::list l;

for(int i = 1; i < argc; ++i) { std::cout << "Findings URL©s in " << argv[i] << ":" << std::endl; s.erase(); std::ifstream is(argv[i]); load_file(s, is); boost::regex_split(std::back_inserter(l), s, e); while(l.size()) { s = *(l.begin()); l.pop_front(); std::cout << s << std::endl; } } return 0; }

High Level Class RegEx (Deprecated)

The high level wrapper class RegEx is now deprecated and does not form part of the regular expression standardization proposal. This type still exists, and existing code will continue to compile, however the following documentation is unlikely to be further updated.

#include

The class RegEx provides a high level simpli®ed interface to the regular expression library, this class only handles narrow character strings, and regular expressions always follow the "normal" syntax - that is the same as the perl / ECMAScript synatx.

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typedef bool (*GrepCallback)(const RegEx& expression); typedef bool (*GrepFileCallback)(const char* file, const RegEx& expression); typedef bool (*FindFilesCallback)(const char* file); class RegEx { public: RegEx(); RegEx(const RegEx& o); ~RegEx(); RegEx(const char* c, bool icase = false); explicit RegEx(const std::string& s, bool icase = false); RegEx& operator=(const RegEx& o); RegEx& operator=(const char* p); RegEx& operator=(const std::string& s); unsigned int SetExpression(const char* p, bool icase = false); unsigned int SetExpression(const std::string& s, bool icase = false); std::string Expression()const; // // now matching operators: // bool Match(const char* p, boost::match_flag_type flags = match_default); bool Match(const std::string& s, boost::match_flag_type flags = match_default); bool Search(const char* p, boost::match_flag_type flags = match_default); bool Search(const std::string& s, boost::match_flag_type flags = match_default); unsigned int Grep(GrepCallback cb, const char* p, boost::match_flag_type flags = match_default); unsigned int Grep(GrepCallback cb, const std::string& s, boost::match_flag_type flags = match_default); unsigned int Grep(std::vector& v, const char* p, boost::match_flag_type flags = match_default); unsigned int Grep(std::vector& v, const std::string& s, boost::match_flag_type flags = match_default); unsigned int Grep(std::vector& v, const char* p, boost::match_flag_type flags = match_default); unsigned int Grep(std::vector& v, const std::string& s, boost::match_flag_type flags = match_default); unsigned int GrepFiles(GrepFileCallback cb, const char* files, bool recurse = false, boost::match_flag_type flags = match_default); unsigned int GrepFiles(GrepFileCallback cb, const std::string& files, bool recurse = false, boost::match_flag_type flags = match_default); unsigned int FindFiles(FindFilesCallback cb, const char* files, bool recurse = false, boost::match_flag_type flags = match_default); unsigned int FindFiles(FindFilesCallback cb, const std::string& files, bool recurse = false, boost::match_flag_type flags = match_default); std::string Merge(const std::string& in, const std::string& fmt, bool copy = true, boost::match_flag_type flags = match_default); std::string Merge(const char* in, const char* fmt, bool copy = true, boost::match_flag_type flags = match_default); unsigned Split(std::vector& v, std::string& s, boost::match_flag_type flags = match_default, unsigned max_count = ~0); // // now operators for returning what matched in more detail: // unsigned int Position(int i = 0)const; unsigned int Length(int i = 0)const; bool Matched(int i = 0)const; unsigned int Line()const;

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unsigned int Marks() const; std::string What(int i)const; std::string operator[](int i)const ;

static const unsigned int npos; };

Member functions for class RegEx are de®ned as follows:

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Member Description

RegEx(); Default constructor, constructs an instance of RegEx without any valid expression.

RegEx(const RegEx& o); Copy constructor, all the properties of parameter o are copied.

RegEx(const char* c, bool icase = false); Constructs an instance of RegEx, setting the expression to c, if icase is true then matching is insensitive to case, otherwise it is sensitive to case. Throws bad_expression on failure.

RegEx(const std::string& s, bool icase = false); Constructs an instance of RegEx, setting the expression to s, if icase is true then matching is insensitive to case, otherwise it is sensitive to case. Throws bad_expression on failure.

RegEx& operator=(const RegEx& o); Default assignment operator.

RegEx& operator=(const char* p); Assignment operator, equivalent to calling SetExpression(p, false). Throws bad_expression on failure.

RegEx& operator=(const std::string& s); Assignment operator, equivalent to calling SetExpression(s, false). Throws bad_expression on failure. unsigned int SetExpression(constchar* p, bool Sets the current expression to p, if icase is true then matching icase = false); is insensitive to case, otherwise it is sensitive to case. Throws bad_expression on failure. unsigned int SetExpression(const std::string& Sets the current expression to s, if icase is true then matching s, bool icase = false); is insensitive to case, otherwise it is sensitive to case. Throws bad_expression on failure. std::string Expression()const; Returns a copy of the current regular expression. bool Match(const char* p, boost::match_flag_type Attempts to match the current expression against the text p using flags = match_default); the match ¯ags ¯ags - see match_flag_type. Returns true if the expression matches the whole of the input string. bool Match(const std::string& s, Attempts to match the current expression against the text s using boost::match_flag_type flags = match_default); the match_flag_type ¯ags. Returns true if the expression matches the whole of the input string. bool Search(const char* p, Attempts to ®nd a match for the current expression somewhere boost::match_flag_type flags = match_default); in the text p using the match_flag_type ¯ags. Returns true if the match succeeds. bool Search(const std::string& s, Attempts to ®nd a match for the current expression somewhere boost::match_flag_type flags = match_default); in the text s using the match_flag_type ¯ags. Returns true if the match succeeds. unsigned int Grep(GrepCallback cb, const char* Finds all matches of the current expression in the text p using p, boost::match_flag_type flags = match_de- the match_flag_type ¯ags. For each match found calls the fault); call-back function cb as: cb(*this); If at any stage the callback function returns false then the grep operation terminates, otherwise continues until no further matches are found. Returns the number of matches found.

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Member Description unsigned int Grep(GrepCallback cb, const Finds all matches of the current expression in the text s using std::string& s, boost::match_flag_type flags = the match_flag_type ¯ags. For each match found calls the match_default); call-back function cb as: cb(*this); If at any stage the callback function returns false then the grep operation terminates, otherwise continues until no further matches are found. Returns the number of matches found. unsigned int Grep(std::vector& v, Finds all matches of the current expression in the text p using const char* p, boost::match_flag_type flags = the match_flag_type ¯ags. For each match pushes a copy of match_default); what matched onto v. Returns the number of matches found. unsigned int Grep(std::vector& v, Finds all matches of the current expression in the text s using const std::string& s, boost::match_flag_type the match_flag_type ¯ags. For each match pushes a copy of flags = match_default); what matched onto v. Returns the number of matches found. unsigned int Grep(std::vector& v, Finds all matches of the current expression in the text p using const char* p, boost::match_flag_type flags = the match_flag_type ¯ags. For each match pushes the starting match_default); index of what matched onto v. Returns the number of matches found. unsigned int Grep(std::vector& v, Finds all matches of the current expression in the text s using const std::string& s, boost::match_flag_type the match_flag_type ¯ags. For each match pushes the starting flags = match_default); index of what matched onto v. Returns the number of matches found. unsigned int GrepFiles(GrepFileCallback cb, Finds all matches of the current expression in the ®les ®les using const char* files, bool recurse = false, the match_flag_type ¯ags. For each match calls the call-back boost::match_flag_type flags = match_default); function cb. If the call-back returns false then the algorithm returns without considering further matches in the current ®le, or any further ®les.

The parameter ®les can include wild card characters ©*© and ©?©, if the parameter recurse is true then searches sub-directories for matching ®le names.

Returns the total number of matches found.

May throw an exception derived from std::runtime_error if ®le io fails. unsigned int GrepFiles(GrepFileCallback cb, Finds all matches of the current expression in the ®les ®les using const std::string& files, bool recurse = false, the match_flag_type ¯ags. For each match calls the call-back boost::match_flag_type flags = match_default); function cb.

If the call-back returns false then the algorithm returns without considering further matches in the current ®le, or any further ®les.

The parameter ®les can include wild card characters ©*© and ©?©, if the parameter recurse is true then searches sub-directories for matching ®le names.

Returns the total number of matches found.

May throw an exception derived from std::runtime_error if ®le io fails.

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Member Description unsigned int FindFiles(FindFilesCallback cb, Searches ®les to ®nd all those which contain at least one match const char* files, bool recurse = false, of the current expression using the match_flag_type ¯ags. boost::match_flag_type flags = match_default); For each matching ®le calls the call-back function cb. If the call-back returns false then the algorithm returns without considering any further ®les.

The parameter ®les can include wild card characters ©*© and ©?©, if the parameter recurse is true then searches sub-directories for matching ®le names.

Returns the total number of ®les found.

May throw an exception derived from std::runtime_error if ®le io fails. unsigned int FindFiles(FindFilesCallback cb, Searches ®les to ®nd all those which contain at least one match const std::string& files, bool recurse = false, of the current expression using the match_flag_type ¯ags. boost::match_flag_type flags = match_default); For each matching ®le calls the call-back function cb.

If the call-back returns false then the algorithm returns without considering any further ®les.

The parameter ®les can include wild card characters ©*© and ©?©, if the parameter recurse is true then searches sub-directories for matching ®le names.

Returns the total number of ®les found.

May throw an exception derived from std::runtime_error if ®le io fails. std::string Merge(const std::string& in, const Performs a search and replace operation: searches through the std::string& fmt, bool copy = true, string in for all occurrences of the current expression, for each boost::match_flag_type flags = match_default); occurrence replaces the match with the format string fmt. Uses ¯ags to determine what gets matched, and how the format string should be treated. If copy is true then all unmatched sections of input are copied unchanged to output, if the ¯ag format_®rst_only is set then only the ®rst occurance of the pattern found is replaced. Returns the new string. See also format string syntax, and match_flag_type. std::string Merge(const char* in, const char* Performs a search and replace operation: searches through the fmt, bool copy = true, boost::match_flag_type string in for all occurrences of the current expression, for each flags = match_default); occurrence replaces the match with the format string fmt. Uses ¯ags to determine what gets matched, and how the format string should be treated. If copy is true then all unmatched sections of input are copied unchanged to output, if the ¯ag format_®rst_only is set then only the ®rst occurance of the pattern found is replaced. Returns the new string. See also format string syntax, and match_flag_type.

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Member Description

unsigned Split(std::vector& v, Splits the input string and pushes each one onto the vector. If std::string& s, boost::match_flag_type flags = the expression contains no marked sub-expressions, then one match_default, unsigned max_count = ~0); string is outputted for each section of the input that does not match the expression. If the expression does contain marked sub-expressions, then outputs one string for each marked sub- expression each time a match occurs. Outputs no more than max_count strings. Before returning, deletes from the input string s all of the input that has been processed (all of the string if max_count was not reached). Returns the number of strings pushed onto the vector.

unsigned int Position(int i = 0)const; Returns the position of what matched sub-expression i. If i = 0 then returns the position of the whole match. Returns RegEx::npos if the supplied index is invalid, or if the speci®ed sub-expression did not participate in the match.

unsigned int Length(int i = 0)const; Returns the length of what matched sub-expression i. If i = 0 then returns the length of the whole match. Returns RegEx::npos if the supplied index is invalid, or if the speci®ed sub-expression did not participate in the match.

bool Matched(int i = 0)const; Returns true if sub-expression i was matched, false otherwise.

unsigned int Line()const; Returns the line on which the match occurred, indexes start from 1 not zero, if no match occurred then returns RegEx::npos.

unsigned int Marks() const; Returns the number of marked sub-expressions contained in the expression. Note that this includes the whole match (sub-expression zero), so the value returned is always >= 1.

std::string What(int i)const; Returns a copy of what matched sub-expression i. If i = 0 then returns a copy of the whole match. Returns a null string if the index is invalid or if the speci®ed sub-expression did not participate in a match.

std::string operator[](int i)const ; Returns what(i); Can be used to simplify access to sub-expression matches, and make usage more perl-like.

Internal Details Unicode Iterators

Synopsis

#include

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template class u32_to_u16_iterator;

template class u16_to_u32_iterator;

template class u32_to_u8_iterator;

template class u8_to_u32_iterator;

template class utf16_output_iterator;

template class utf8_output_iterator;

Description

This header contains a selection of iterator adaptors that make a sequence of characters in one encoding "look like" a read-only sequence of characters in another encoding.

template class u32_to_u16_iterator { u32_to_u16_iterator(); u32_to_u16_iterator(BaseIterator start_position);

// Other standard BidirectionalIterator members here... };

A Bidirectional iterator adapter that makes an underlying sequence of UTF32 characters look like a (read-only) sequence of UTF16 characters. The UTF16 characters are encoded in the platforms native byte order.

template class u16_to_u32_iterator { u16_to_u32_iterator(); u16_to_u32_iterator(BaseIterator start_position); u16_to_u32_iterator(BaseIterator start_position, BaseIterator start_range, BaseIterat↵ or end_range);

// Other standard BidirectionalIterator members here... };

A Bidirectional iterator adapter that makes an underlying sequence of UTF16 characters (in the platforms native byte order) look like a (read-only) sequence of UTF32 characters.

The three-arg constructor of this class takes the start and end of the underlying sequence as well as the position to start iteration from. This constructor validates that the underlying sequence has validly encoded endpoints: this prevents accidently increment- ing/decrementing past the end of the underlying sequence as a result of invalid UTF16 code sequences at the endpoints of the underlying range.

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template class u32_to_u8_iterator { u32_to_u8_iterator(); u32_to_u8_iterator(BaseIterator start_position);

// Other standard BidirectionalIterator members here... };

A Bidirectional iterator adapter that makes an underlying sequence of UTF32 characters look like a (read-only) sequence of UTF8 characters.

template class u8_to_u32_iterator { u8_to_u32_iterator(); u8_to_u32_iterator(BaseIterator start_position); u8_to_u32_iterator(BaseIterator start_position, BaseIterator start_range, BaseIterat↵ or end_range);

// Other standard BidirectionalIterator members here... };

A Bidirectional iterator adapter that makes an underlying sequence of UTF8 characters look like a (read-only) sequence of UTF32 characters.

The three-arg constructor of this class takes the start and end of the underlying sequence as well as the position to start iteration from. This constructor validates that the underlying sequence has validly encoded endpoints: this prevents accidently increment- ing/decrementing past the end of the underlying sequence as a result of invalid UTF8 code sequences at the endpoints of the underlying range.

template class utf16_output_iterator { utf16_output_iterator(const BaseIterator& b); utf16_output_iterator(const utf16_output_iterator& that); utf16_output_iterator& operator=(const utf16_output_iterator& that);

// Other standard OutputIterator members here... };

Simple OutputIterator adapter - accepts UTF32 values as input, and forwards them to BaseIterator b as UTF16. Both UTF32 and UTF16 values are in native byte order.

template class utf8_output_iterator { utf8_output_iterator(const BaseIterator& b); utf8_output_iterator(const utf8_output_iterator& that); utf8_output_iterator& operator=(const utf8_output_iterator& that);

// Other standard OutputIterator members here... };

Simple OutputIterator adapter - accepts UTF32 values as input, and forwards them to BaseIterator b as UTF8. The UTF32 input values must be in native byte order.

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Background Information Headers

There are two main headers used by this library: provides full access to the main template library, while provides access to the (deprecated) high level class RegEx, and the POSIX API functions.

There is also a header containing only forward declarations for use when an interface is dependent upon basic_regex, but otherwise does not need the full de®nitions. Localization

Boost.Regex provides extensive support for run-time localization, the localization model used can be split into two parts: front-end and back-end.

Front-end localization deals with everything which the user sees - error messages, and the regular expression syntax itself. For example a French application could change [[:word:]] to [[:mot:]] and \w to \m. Modifying the front end locale requires active support from the developer, by providing the library with a message catalogue to load, containing the localized strings. Front-end locale is affected by the LC_MESSAGES category only.

Back-end localization deals with everything that occurs after the expression has been parsed - in other words everything that the user does not see or interact with directly. It deals with case conversion, collation, and character class membership. The back-end locale does not require any intervention from the developer - the library will acquire all the information it requires for the current locale from the underlying operating system / run time library. This means that if the program user does not interact with regular expressions directly - for example if the expressions are embedded in your C++ code - then no explicit localization is required, as the library will take care of everything for you. For example embedding the expression [[:word:]]+ in your code will always match a whole word, if the program is run on a machine with, for example, a Greek locale, then it will still match a whole word, but in Greek characters rather than Latin ones. The back-end locale is affected by the LC_TYPE and LC_COLLATE categories.

There are three separate localization mechanisms supported by Boost.Regex:

Win32 localization model.

This is the default model when the library is compiled under Win32, and is encapsulated by the traits class w32_regex_traits. When this model is in effect each basic_regex object gets it©s own LCID, by default this is the users default setting as returned by GetUserDefaultLCID, but you can call imbue on the basic_regex object to set it©s locale to some other LCID if you wish. All the settings used by Boost.Regex are acquired directly from the operating system bypassing the C run time library. Front-end localization requires a resource dll, containing a string table with the user-de®ned strings. The traits class exports the function:

static std::string set_message_catalogue(const std::string& s); which needs to be called with a string identifying the name of the resource dll, before your code compiles any regular expressions (but not necessarily before you construct any basic_regex instances):

boost::w32_regex_traits::set_message_catalogue("mydll.dll");

The library provides full Unicode support under NT, under Windows 9x the library degrades gracefully - characters 0 to 255 are supported, the remainder are treated as "unknown" graphic characters.

C localization model.

This model has been deprecated in favor of the C++ locale for all non-Windows compilers that support it. This locale is encapsulated by the traits class c_regex_traits, Win32 users can force this model to take effect by de®ning the pre-processor symbol BOOST_REGEX_USE_C_LOCALE. When this model is in effect there is a single global locale, as set by setlocale. All settings are acquired from your run time library, consequently Unicode support is dependent upon your run time library implementation.

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Front end localization is not supported.

Note that calling setlocale invalidates all compiled regular expressions, calling setlocale(LC_ALL, "C") will make this library behave equivalent to most traditional regular expression libraries including version 1 of this library.

C++ localization model.

This model is the default for non-Windows compilers.

When this model is in effect each instance of basic_regex has its own instance of std::locale, class basic_regex also has a member function imbue which allows the locale for the expression to be set on a per-instance basis. Front end localization requires a POSIX message catalogue, which will be loaded via the std::messages facet of the expression©s locale, the traits class exports the symbol:

static std::string set_message_catalogue(const std::string& s); which needs to be called with a string identifying the name of the message catalogue, before your code compiles any regular expressions (but not necessarily before you construct any basic_regex instances):

boost::cpp_regex_traits::set_message_catalogue("mycatalogue");

Note that calling basic_regex<>::imbue will invalidate any expression currently compiled in that instance of basic_regex.

Finally note that if you build the library with a non-default localization model, then the appropriate pre-processor symbol (BOOST_REGEX_USE_C_LOCALE or BOOST_REGEX_USE_CPP_LOCALE) must be de®ned both when you build the support library, and when you include or in your code. The best way to ensure this is to add the #de®ne to .

Providing a message catalogue

In order to localize the front end of the library, you need to provide the library with the appropriate message strings contained either in a resource dll©s string table (Win32 model), or a POSIX message catalogue (C++ models). In the latter case the messages must appear in message set zero of the catalogue. The messages and their id©s are as follows:

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Message id Meaning De- fault value

101 The character used to start a sub-expres- "(" sion.

102 The character used to end a sub-expres- ")" sion declaration.

103 The character used to denote an end of "$" line assertion.

104 The character used to denote the start "^" of line assertion.

105 The character used to denote the "." "match any character expression".

106 The match zero or more times repeti- "*" tion operator.

107 The match one or more repetition oper- "+" ator.

108 The match zero or one repetition oper- "?" ator.

109 The character set opening character. "["

110 The character set closing character. "]"

111 The alternation operator. "|"

112 The escape character. "\"

113 The hash character (not currently "#" used).

114 The range operator. "-"

115 The repetition operator opening charac- "{" ter.

116 The repetition operator closing charac- "}" ter.

117 The digit characters. "0123456789"

118 The character which when preceded "b" by an escape character represents the word boundary assertion.

119 The character which when preceded "B" by an escape character represents the non-word boundary assertion.

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Message id Meaning De- fault value

120 The character which when preceded "<" by an escape character represents the word-start boundary assertion.

121 The character which when preceded ">" by an escape character represents the word-end boundary assertion.

122 The character which when preceded "w" by an escape character represents any word character.

123 The character which when preceded "W" by an escape character represents a non-word character.

124 The character which when preceded "ÁA" by an escape character represents a start of buffer assertion.

126 The newline character. "\n"

127 The comma separator. ","

128 The character which when preceded "a" by an escape character represents the bell character.

129 The character which when preceded "f" by an escape character represents the form feed character.

130 The character which when preceded "n" by an escape character represents the newline character.

131 The character which when preceded "r" by an escape character represents the carriage return character.

132 The character which when preceded "t" by an escape character represents the tab character.

133 The character which when preceded "v" by an escape character represents the vertical tab character.

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Message id Meaning De- fault value

134 The character which when preceded "x" by an escape character represents the start of a hexadecimal character constant.

135 The character which when preceded "c" by an escape character represents the start of an ASCII escape character.

136 The colon character. ":"

137 The equals character. "="

138 The character which when preceded "e" by an escape character represents the ASCII escape character.

139 The character which when preceded "l" by an escape character represents any lower case character.

140 The character which when preceded "L" by an escape character represents any non-lower case character.

141 The character which when preceded "u" by an escape character represents any upper case character.

142 The character which when preceded "U" by an escape character represents any non-upper case character.

143 The character which when preceded "s" by an escape character represents any space character.

144 The character which when preceded "S" by an escape character represents any non-space character.

145 The character which when preceded "d" by an escape character represents any digit character.

146 The character which when preceded "D" by an escape character represents any non-digit character.

147 The character which when preceded "E" by an escape character represents the end quote operator.

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Message id Meaning De- fault value

148 The character which when preceded "Q" by an escape character represents the start quote operator.

149 The character which when preceded "X" by an escape character represents a Unicode combining character sequence.

150 The character which when preceded "C" by an escape character represents any single character.

151 The character which when preceded "Z" by an escape character represents end of buffer operator.

152 The character which when preceded "G" by an escape character represents the continuation assertion.

153 The character which when preceeded ! by (? indicates a zero width negated forward lookahead assert.

Custom error messages are loaded as follows:

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Message ID Error message ID Default string

201 REG_NOMATCH "No match"

202 REG_BADPAT "Invalid regular expression"

203 REG_ECOLLATE "Invalid collation character"

204 REG_ECTYPE "Invalid character class name"

205 REG_EESCAPE "Trailing backslash"

206 REG_ESUBREG "Invalid back reference"

207 REG_EBRACK "Unmatched [ or " [208 REG_EPAR- "Un- EN matched ( or \("

209 REG_EBRACE "Unmatched \{"

210 REG_BADBR "Invalid content of \{\}"

211 REG_ERANGE "Invalid range end"

212 REG_ESPACE "Memory exhausted"

213 REG_BADRPT "Invalid preceding regular expression"

214 REG_EEND "Premature end of regular expression"

215 REG_ESIZE "Regular expression too big"

216 REG_ERPAREN "Unmatched ) or \)"

217 REG_EMPTY "Empty expression"

218 REG_E_UNKNOWN "Unknown error"

Custom character class names are loaded as followed:

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Message ID Description Equivalent default class name

300 The character class name for alphanumer- "alnum" ic characters.

301 The character class name for alphabetic "alpha" characters.

302 The character class name for control "cntrl" characters.

303 The character class name for digit charac- "digit" ters.

304 The character class name for graphics "graph" characters.

305 The character class name for lower case "lower" characters.

306 The character class name for printable "print" characters.

307 The character class name for punctuation "punct" characters.

308 The character class name for space char- "space" acters.

309 The character class name for upper case "upper" characters.

310 The character class name for hexadecimal "xdigit" characters.

311 The character class name for blank char- "blank" acters.

312 The character class name for word charac- "word" ters.

313 The character class name for Unicode "unicode" characters.

Finally, custom collating element names are loaded starting from message id 400, and terminating when the ®rst load thereafter fails. Each message looks something like: "tagname string" where tagname is the name used inside [[.tagname.]] and string is the actual text of the collating element. Note that the value of collating element [[.zero.]] is used for the conversion of strings to numbers - if you replace this with another value then that will be used for string parsing - for example use the Unicode character 0x0660 for [[.zero.]] if you want to use Unicode Arabic-Indic digits in your regular expressions in place of Latin digits.

Note that the POSIX de®ned names for character classes and collating elements are always available - even if custom names are de®ned, in contrast, custom error messages, and custom syntax messages replace the default ones.

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Thread Safety

The Boost.Regex library is thread safe when Boost is: you can verify that Boost is in thread safe mode by checking to see if BOOST_HAS_THREADS is de®ned: this macro is set automatically by the con®g system when threading support is turned on in your compiler.

Class basic_regex and its typedefs regex and wregex are thread safe, in that compiled regular expressions can safely be shared between threads. The matching algorithms regex_match, regex_search, and regex_replace are all re-entrant and thread safe. Class match_results is now thread safe, in that the results of a match can be safely copied from one thread to another (for example one thread may ®nd matches and push match_results instances onto a queue, while another thread pops them off the other end), otherwise use a separate instance of match_results per thread.

The POSIX API functions are all re-entrant and thread safe, regular expressions compiled with regcomp can also be shared between threads.

The class RegEx is only thread safe if each thread gets its own RegEx instance (apartment threading) - this is a consequence of RegEx handling both compiling and matching regular expressions.

Finally note that changing the global locale invalidates all compiled regular expressions, therefore calling set_locale from one thread while another uses regular expressions will produce unpredictable results.

There is also a requirement that there is only one thread executing prior to the start of main(). Test and Example Programs

Test Programs regress:

A regression test application that gives the matching/searching algorithms a full workout. The presence of this program is your guarantee that the library will behave as claimed - at least as far as those items tested are concerned - if anyone spots anything that isn©t being tested I©d be glad to hear about it.

Files:

· main.cpp

· basic_tests.cpp

· test_alt.cpp

· test_anchors.cpp

· test_asserts.cpp

· test_backrefs.cpp

· test_deprecated.cpp

· test_emacs.cpp

· test_escapes.cpp

· test_grep.cpp

· test_icu.cpp

· test_locale.cpp

· test_mfc.cpp

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· test_non_greedy_repeats.cpp

· test_operators.cpp

· test_overloads.cpp

· test_perl_ex.cpp

· test_replace.cpp

· test_sets.cpp

· test_simple_repeats.cpp

· test_tricky_cases.cpp

· test_unicode.cpp bad_expression_test:

Veri®es that "bad" regular expressions don©t cause the matcher to go into in®nite loops, but to throw an exception instead.

Files: bad_expression_test.cpp. recursion_test:

Files: recursion_test.cpp. concepts:

Veri®es that the library meets all documented concepts (a compile only test).

Files: concept_check.cpp. captures_test:

Test code for captures.

Files: captures_test.cpp.

Example programs grep

A simple grep implementation, run with the -h command line option to ®nd out its usage.

Files: grep.cpp timer.exe

A simple interactive expression matching application, the results of all matches are timed, allowing the programmer to optimize their regular expressions where performance is critical.

Files: regex_timer.cpp.

Code snippets

The snippets examples contain the code examples used in the documentation: captures_example.cpp: Demonstrates the use of captures.

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XML to PDF by RenderX XEP XSL-FO Formatter, visit us at http://www.renderx.com/ Boost.Regex credit_card_example.cpp: Credit card number formatting code. partial_regex_grep.cpp: Search example using partial matches. partial_regex_match.cpp: regex_match example using partial matches. regex_iterator_example.cpp: Iterating through a series of matches. regex_match_example.cpp: ftp based regex_match example. regex_merge_example.cpp: regex_merge example: converts a C++ ®le to syntax highlighted HTML. regex_replace_example.cpp: regex_replace example: converts a C++ ®le to syntax highlighted HTML regex_search_example.cpp: regex_search example: searches a cpp ®le for class de®nitions. regex_token_iterator_eg_1.cpp: split a string into a series of tokens. regex_token_iterator_eg_2.cpp: enumerate the linked URL©s in a HTML ®le.

The following are deprecated: regex_grep_example_1.cpp: regex_grep example 1: searches a cpp ®le for class de®nitions. regex_grep_example_2.cpp: regex_grep example 2: searches a cpp ®le for class de®nitions, using a global callback function. regex_grep_example_3.cpp: regex_grep example 2: searches a cpp ®le for class de®nitions, using a bound member function callback. regex_grep_example_4.cpp: regex_grep example 2: searches a cpp ®le for class de®nitions, using a C++ Builder closure as a callback. regex_split_example_1.cpp: regex_split example: split a string into tokens. regex_split_example_2.cpp : regex_split example: spit out linked URL©s. References and Further Information

Short tutorials on regular expressions can be found here and here.

Boost.Regex forms the basis for the regular expression chapter of the Technical Report on C++ Library Extensions.

The Open Unix Speci®cation contains a wealth of useful material, including the POSIX regular expression syntax.

The Pattern Matching Pointers site is a "must visit" resource for anyone interested in pattern matching.

Glimpse and Agrep, use a simpli®ed regular expression syntax to achieve faster search times.

Udi Manber and Ricardo Baeza-Yates both have a selection of useful pattern matching papers available from their respective web sites. FAQ

A. If you embed regular expressions in C++ code, then remember that escape characters are processed twice: once by the C++ compiler, and once by the Boost.Regex expression compiler, so to pass the regular expression \d+ to Boost.Regex, you need to embed "\d+" in your code. Likewise to match a literal backslash you will need to embed "\\" in your code.

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A. The algorithm regex_match only succeeds if the expression matches all of the text, if you want to ®nd a sub-string within the text that matches the expression then use regex_search instead.

Q. Why does using parenthesis in a POSIX regular expression change the result of a match?

A. For POSIX (extended and basic) regular expressions, but not for perl regexes, parentheses don©t only mark; they determine what the best match is as well. When the expression is compiled as a POSIX basic or extended regex then Boost.Regex follows the POSIX standard leftmost longest rule for determining what matched. So if there is more than one possible match after considering the whole expression, it looks next at the ®rst sub-expression and then the second sub-expression and so on. So...

"(0*)([0-9]*)" against "00123" would produce $1 = "00" $2 = "123" where as

"0*([0-9])*" against "00123" would produce $1 = "00123"

If you think about it, had $1 only matched the "123", this would be "less good" than the match "00123" which is both further to the left and longer. If you want $1 to match only the "123" part, then you need to use something like:

"0*([1-9][0-9]*)" as the expression.

A. The POSIX standard speci®es that character range expressions are locale sensitive - so for example the expression [A-Z] will match any collating element that collates between ©A© and ©Z©. That means that for most locales other than "C" or "POSIX", [A-Z] would match the single character ©t© for example, which is not what most people expect - or at least not what most people have come to expect from regular expression engines. For this reason, the default behaviour of Boost.Regex (perl mode) is to turn locale sensitive collation off by not setting the regex_constants::collate compile time ¯ag. However if you set a non-default compile time ¯ag - for example regex_constants::extended or regex_constants::basic, then locale dependent collation will be enabled, this also applies to the POSIX API functions which use either regex_constants::extended or regex_constants::basic internally. [Note - when regex_constants::nocollate in effect, the library behaves "as if" the LC_COLLATE locale category were always "C", regardless of what its actually set to - end note].

Q. Why are there no throw speci®cations on any of the functions? What exceptions can the library throw?

A. Not all compilers support (or honor) throw speci®cations, others support them but with reduced ef®ciency. Throw speci®cations may be added at a later date as compilers begin to handle this better. The library should throw only three types of exception: [boost::regex_error] can be thrown by basic_regex when compiling a regular expression, std::runtime_error can be thrown when a call to basic_regex::imbue tries to open a message catalogue that doesn©t exist, or when a call to regex_search or regex_match results in an "everlasting" search, or when a call to RegEx::GrepFiles or RegEx::FindFiles tries to open a ®le that cannot be opened, ®nally std::bad_alloc can be thrown by just about any of the functions in this library.

A. These versions may or may not be available depending upon the capabilities of your compiler, the rules determining the format of these functions are quite complex - and only the versions visible to a standard compliant compiler are given in the help. To ®nd out what your compiler supports, run through your C++ pre-processor, and search the output ®le for the function that you are interested in. Note however, that very few current compilers still have problems with these overloaded functions. Performance

The performance of Boost.Regex in both recursive and non-recursive modes should be broadly comparable to other regular expression libraries: recursive mode is slightly faster (especially where memory allocation requires thread synchronisation), but not by much. The following pages compare Boost.Regex with various other regular expression libraries for the following compilers:

· Visual Studio.Net 2003 (recursive Boost.Regex implementation).

· Gcc 3.2 (cygwin) (non-recursive Boost.Regex implementation).

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Standards Conformance

C++

Boost.Regex is intended to conform to the Technical Report on C++ Library Extensions.

ECMAScript / JavaScript

All of the ECMAScript regular expression syntax features are supported, except that:

The escape sequence \u matches any upper case character (the same as [[:upper:]]) rather than a Unicode escape sequence; use \x{DDDD} for Unicode escape sequences.

Perl

Almost all Perl features are supported, except for:

(?{code}) Not implementable in a compiled strongly typed language.

(??{code}) Not implementable in a compiled strongly typed language.

(*VERB) The backtracking control verbs are not recognised or implemented at this time.

In addition the following features behave slightly differently from Perl:

^ $ \Z These recognise any line termination sequence, and not just \n: see the Unicode requirements below.

POSIX

All the POSIX basic and extended regular expression features are supported, except that:

No character collating names are recognized except those speci®ed in the POSIX standard for the C locale, unless they are explicitly registered with the traits class.

Character equivalence classes ( [[=a=]] etc) are probably buggy except on Win32. Implementing this feature requires knowledge of the format of the string sort keys produced by the system; if you need this, and the default implementation doesn©t work on your platform, then you will need to supply a custom traits class.

Unicode

The following comments refer to Unicode Technical Standard #18: Unicode Regular Expressions version 11.

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Item Feature Support

1.1 Hex Notation Yes: use \x{DDDD} to refer to code point UDDDD.

1.2 Character Properties All the names listed under the General Category Property are supported. Script names and Other Names are not currently supported.

1.3 Subtraction and Intersection Indirectly support by forward-lookahead:

(?=[[:X:]])[[:Y:]]

Gives the intersection of character properties X and Y.

(?![[:X:]])[[:Y:]]

Gives everything in Y that is not in X (subtraction).

1.4 Simple Word Boundaries Conforming: non-spacing marks are in- cluded in the set of word characters.

1.5 Caseless Matching Supported, note that at this level, case transformations are 1:1, many to many case folding operations are not supported (for example "û" to "SS").

1.6 Line Boundaries Supported, except that "." matches only one character of "\r\n". Other than that word boundaries match correctly; including not matching in the middle of a "\r\n" sequence.

1.7 Code Points Supported: provided you use the u32* algorithms, then UTF-8, UTF-16 and UTF- 32 are all treated as sequences of 32-bit code points.

2.1 Canonical Equivalence Not supported: it is up to the user of the library to convert all text into the same canonical form as the regular expression.

2.2 Default Grapheme Clusters Not supported.

2.3Default Word Boundaries Not supported.

2.4 Default Loose Matches Not Supported.

2.5 Named Properties Supported: the expression "[[:name:]]" or \N{name} matches the named character "name".

2.6 Wildcard properties Not Supported.

3.1 Tailored Punctuation. Not Supported.

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Item Feature Support

3.2 Tailored Grapheme Clusters Not Supported.

3.3 Tailored Word Boundaries. Not Supported.

3.4 Tailored Loose Matches Partial support: [[=c=]] matches characters with the same primary equivalence class as "c".

3.5 Tailored Ranges Supported: [a-b] matches any character that collates in the range a to b, when the expression is constructed with the collate ¯ag set.

3.6 Context Matches Not Supported.

3.7 Incremental Matches Supported: pass the ¯ag match_partial to the regex algorithms.

3.8 Unicode Set Sharing Not Supported.

3.9 Possible Match Sets Not supported, however this information is used internally to optimise the matching of regular expressions, and return quickly if no match is possible.

3.10 Folded Matching Partial Support: It is possible to achieve a similar effect by using a custom regular expression traits class.

3.11 Custom Submatch Evaluation Not Supported.

Redistributables

If you are using Microsoft or Borland C++ and link to a dll version of the run time library, then you can choose to also link to a dll version of Boost.Regex by de®ning the symbol BOOST_REGEX_DYN_LINK when you compile your code. While these dll©s are redistributable, there are no "standard" versions, so when installing on the users PC, you should place these in a directory private to your application, and not in the PC©s directory path. Note that if you link to a static version of your run time library, then you will also link to a static version of Boost.Regex and no dll©s will need to be distributed. The possible Boost.Regex dll and library names are computed according to the formula given in the getting started guide.

Note: you can disable automatic library selection by de®ning the symbol BOOST_REGEX_NO_LIB when compiling, this is useful if you want to build Boost.Regex yourself in your IDE, or if you need to debug Boost.Regex. Acknowledgements

The author can be contacted at john - at - johnmaddock.co.uk; the home page for this library is at www.boost.org.

I am indebted to Robert Sedgewick©s "Algorithms in C++" for forcing me to think about algorithms and their performance, and to the folks at boost for forcing me to think, period.

Eric Niebler, author of Boost.Expressive and the GRETA regular expression component, has shared several important ideas, in a series of long discussions.

Pete Becker, of Roundhouse Consulting, Ltd., has helped enormously with the standardisation proposal language.

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The following people have all contributed useful comments or ®xes: Dave Abrahams, Mike Allison, Edan Ayal, Jayashree Balasub- ramanian, Jan Bölsche, Beman Dawes, Paul Baxter, David Bergman, David Dennerline, Edward Diener, Peter Dimov, Robert Dunn, Fabio Forno, Tobias Gabrielsson, Rob Gillen, Marc Gregoire, Chris Hecker, Nick Hodapp, Jesse Jones, Martin Jost, Boris Krasnovskiy, Jan Hermelink, Max Leung, Wei-hao Lin, Jens Maurer, Richard Peters, Heiko Schmidt, Jason Shirk, Gerald Slacik, Scobie Smith, Mike Smyth, Alexander Sokolovsky, Hervé Poirier, Michael Raykh, Marc Recht, Scott VanCamp, Bruno Voigt, Alexey Voinov, Jerry Waldorf, Rob Ward, Lealon Watts, John Wismar, Thomas Witt and Yuval Yosef.

I am also grateful to the manuals supplied with the Henry Spencer, PCRE, Perl and GNU regular expression libraries - wherever possible I have tried to maintain compatibility with these libraries and with the POSIX standard - the code however is entirely my own, including any bugs! I can absolutely guarantee that I will not ®x any bugs I don©t know about, so if you have any comments or spot any bugs, please get in touch. History

Currently open issues can be viewed here.

All issues including closed ones can be viewed here.

Boost-1.54

Fixed issue #8569.

Boost-1.53

Fixed Issues: #7744, #7644.

Boost-1.51

Fixed issues: #589, #7084, #7032, #6346.

Boost-1.50

Fixed issue with (?!) not being a valid expression, and updated docs on what constitutes a valid conditional expression.

Boost-1.48

Fixed issues: #698, #5835, #5958, #5736.

Boost 1.47

Fixed issues: #5223, #5353, #5363, #5462, #5472, #5504.

Boost 1.44

Fixed issues: #4309, #4215, #4212, #4191, #4132, #4123, #4114, #4036, #4020, #3941, #3902, #3890

Boost 1.42

· Added support for Functors rather than strings as format expressions.

· Improved error reporting when throwing exceptions to include better more relevant information.

· Improved performance and reduced stack usage of recursive expressions.

· Fixed tickets #2802, #3425, #3507, #3546, #3631, #3632, #3715, #3718, #3763, #3764

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Boost 1.40

· Added support for many Perl 5.10 syntax elements including named sub-expressions, branch resets and recursive regular expressions.

Boost 1.38

· Breaking change: empty expressions, and empty alternatives are now allowed when using the Perl regular expression syntax. This change has been added for Perl compatibility, when the new syntax_option_type no_empty_expressions is set then the old behaviour is preserved and empty expressions are prohibited. This is issue #1081.

· Added support for Perl style ${n} expressions in format strings (issue #2556).

· Added support for accessing the location of sub-expressions within the regular expression string (issue #2269).

· Fixed compiler compatibility issues #2244, #2514, and #2458.

Boost 1.34

· Fix for non-greedy repeats and partial matches not working correctly in some cases.

· Fix for non-greedy repeats on VC++ not working in some cases (bug report 1515830).

· Changed match_results::position() to return a valid result when *this represents a partial match.

· Fixed the grep and egrep options so that the newline character gets treated the same as |.

Boost 1.33.1

· Fixed broken make®les.

· Fixed con®guration setup to allow building with VC7.1 - STLport-4.6.2 when using /Zc:wchar_t.

· Moved declarations class-inline in static_mutex.hpp so that SGI Irix compiler can cope.

· Added needed standard library #includes to ®leiter.hpp, regex_workaround.hpp and cpp_regex_traits.hpp.

· Fixed a bug where non-greedy repeats could in certain strange curcumstances repeat more times than their maximum value.

· Fixed the value returned by basic_regex<>::empty() from a default constructed object.

· Changed the def®nition of regex_error to make it backwards compatible with Boost-1.32.0.

· Disabled external templates for Intel C++ 8.0 and earlier - otherwise unresolved references can occur.

· Rewritten extern template code for gcc so that only speci®c member functions are exported: otherwise strange unresolved references can occur when linking and mixing debug and non-debug code.

· Initialise all the data members of the unicode_iterators: this keeps gcc from issuing needless warnings.

· Ported the ICU integration code to VC6 and VC7.

· Ensured code is STLport debug mode clean.

· Fixed lookbehind assertions so that ®xed length repeats are permitted, and so that regex iteration allows lookbehind to look back before the current search range (into the last match).

· Fixed strange bug with non-greedy repeats inside forward lookahead assertions.

· Enabled negated character classes inside character sets.

· Fixed regression so that [a-z-] is a valid expression again.

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· Fixed bug that allowed some invalid expressions to be accepted.

Boost 1.33.0

· Completely rewritten expression parsing code, and traits class support; now conforms to the standardization proposal.

· Breaking Change: The syntax options that can be passed to basic_regex constructors have been rationalized. The default option (perl) now has a value of zero, and it is now clearly documented which options apply to which regular expression syntax styles (perl, POSIX-extended, POSIX-basic etc). Some of the more esoteric options have now been removed, so there is the possibility that existing code may fail to compile: however equivalent functionality should still be available.

· Breaking Change: POSIX-extended and POSIX-basic regular expressions now enforce the letter of the POSIX standard much more closely than before.

· Added support for (?imsx-imsx) constructs.

· Added support for lookbehind expressions (?<=positive-lookbehind) and (?

· Added support for conditional expressions (?(assertion)true-expresion|false-expression).

· Added MFC/ATL string wrappers.

· Added Unicode support; based on ICU.

· Changed newline support to recognise \f as a line separator (all character types), and \x85 as a line separator for wide characters / Unicode only.

· Added a new format ¯ag format_literal that treats the replace string as a literal, rather than a Perl or Sed style format string.

· Errors are now reported by throwing exceptions of type regex_error. The types used previously - bad_expression and bad_pattern - are now just typedefs for regex_error. Type regex_error has a couple of new members: code() to report an error code rather than a string, and position() to report where in the expression the error occurred.

Boost 1.32.1

Boost 1.31.0

· Completely rewritten pattern matching code - it is now up to 10 times faster than before.

· Reorganized documentation.

· Deprecated all interfaces that are not part of the regular expression standardization proposal.

· Added regex_iterator and regex_token_iterator .

· Added support for Perl style independent sub-expressions.

· Added non-member operators to the sub_match class, so that you can compare sub_match©s with strings, or add them to a string to produce a new string.

· Added experimental support for extended capture information.

· Changed the match ¯ags so that they are a distinct type (not an integer), if you try to pass the match ¯ags as an integer rather than match_¯ag_type to the regex algorithms then you will now get a compiler error.

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